Rule2026-21862
Airworthiness Directives; The Boeing Company Airplanes
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
October 27, 2026
Effective
December 1, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-700, -700C, -800, and -900ER series airplanes. This AD was prompted by a leak through the form-in- place (FiP) gasket at the engine fuel shutoff valve access panel found during a leak check. This AD requires a detailed inspection of the left- and right-side FiP gasket at the engine fuel shutoff valve access panel for correct sealant installation, a fluid leak test of the engine fuel shutoff valve access panels for any leak, and applicable on- condition actions. The FAA is issuing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 91 Issue 206 (Tuesday, October 27, 2026)</title>
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[Federal Register Volume 91, Number 206 (Tuesday, October 27, 2026)]
[Rules and Regulations]
[Pages 67448-67451]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-21862]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-2725; Project Identifier AD-2025-00999-T;
Amendment 39-23497; AD 2026-21-08]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain The Boeing Company Model 737-700, -700C, -800, and -900ER
series airplanes. This AD was prompted by a leak through the form-in-
place (FiP) gasket at the engine fuel shutoff valve access panel found
during a leak check. This AD requires a detailed inspection of the
left- and right-side FiP gasket at the engine fuel shutoff valve access
panel for correct sealant installation, a fluid leak test of the engine
fuel shutoff valve access panels for any leak, and applicable on-
condition actions. The FAA is issuing this AD to address the unsafe
condition on these products.
DATES: This AD is effective December 1, 2026.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of December 1,
2026.
ADDRESSES:
AD Docket: You may examine the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2026-2725; or in person at Docket Operations between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD
docket contains this final rule, any comments received, and other
information. The address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
<bullet> For Boeing material identified in this AD, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; website <a href="http://myboeingfleet.com">myboeingfleet.com</a>.
<bullet> You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St., Des
Moines, WA. For information on the availability of this material at the
FAA, call 206-231-3195. It is also available at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2026-2725.
FOR FURTHER INFORMATION CONTACT: Erica Bayles, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 907-
271-5844; email: <a href="/cdn-cgi/l/email-protection#8eebfce7edefa0eba0eceff7e2ebfdcee8efefa0e9e1f8"><span class="__cf_email__" data-cfemail="3a5f4853595b145f14585b43565f497a5c5b5b145d554c">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain The Boeing
Company Model 737-700, -700C, -800, and -900ER series airplanes. The
NPRM was published in the Federal Register on March 26, 2026 (91 FR
14654). The NPRM was prompted by a leak through
[[Page 67449]]
the FiP gasket at the engine fuel shutoff valve access panel found
during a leak check, completed as part of a nonconformance disposition
for the Boeing Company Model 737-8, 737-9, and 737-8200 airplanes. An
investigation found that the fairing requirements of the engine fuel
shutoff valve access panel caused thin regions of the FiP gasket, which
caused the manufacturer to apply non-permitted sealant after the
initial FiP gasket had cured, resulting in an uneven sealing surface on
the engine fuel shutoff valve access panel and leak. In the NPRM, the
FAA proposed to require a detailed inspection of the left- and right-
side FiP gasket at the engine fuel shutoff valve access panel for
correct sealant installation, a fluid leak test of the engine fuel
shutoff valve access panels for any leak, and applicable on-condition
actions. The FAA is issuing this AD to address incorrect or missing
sealant installation. The unsafe condition, if not addressed, could
result in fuel leaking onto the engine exhaust nozzle and a possible
fire on the ground.
Discussion of Final Airworthiness Directive
Comments
The FAA received comments from an anonymous commenter who supported
the NPRM without change.
The FAA received additional comments from four commenters,
including Aviation Partners Boeing (APB), American Airlines (American),
Southwest Airlines (Southwest), and United Airlines (United). The
following presents the comments received on the NPRM and the FAA's
response to each comment.
Request To Combine Proposed ADs
American requested that the FAA rescind the proposed AD and instead
add the affected airplanes and proposed requirements to another
proposed AD (Docket No. FAA-2026-2716, Project Identifier AD-2025-
00990-T). American noted, although the proposed ADs reference different
service information and different airplane models, both proposed ADs
would mandate similar requirements. American stated consolidating these
actions into a single NPRM would improve clarity and enhance compliance
management without changing the technical intent of the inspection or
impacting airplane airworthiness.
The FAA disagrees with this request. The FAA acknowledges that some
operators may prefer to address the unsafe condition with a single AD;
however, other operators may prefer that the FAA issue two separate
ADs. Additionally, when the manufacturer develops two separate service
bulletins to address an unsafe condition on different airplane models,
proceeding with two separate ADs, in general, allows the FAA to address
the unsafe condition on all airplane models in a timely manner. For
example, if development of one service bulletin is delayed, the
rulemaking process would be delayed for all affected airplane models.
Effect of Winglets on Accomplishment of the Proposed Actions
APB stated that the blended or split scimitar winglets installed
per Supplemental Type Certificate (STC) ST00830SE does not affect
compliance with the proposed requirements.
The FAA agrees that the installation of STC ST00830SE does not
affect the ability to accomplish the actions required by this AD. The
FAA has not changed this AD in this regard.
Request To Clarify Applicability Difference
United requested the FAA clarify why the applicability of the
proposed AD was expanded beyond the effectivity of Boeing Alert
Requirements Bulletin 737-57A1359 RB, dated October 3, 2025 (original
issue of the Boeing Alert Requirements Bulletin). United stated this
clarification would assist operators in understanding the unsafe
condition and ensure consistent implementation across the affected
fleet.
The FAA expanded the applicability of the AD based on a report from
the manufacturer indicating that certain airplanes were incorrectly
excluded from the effectivity of the original issue of the Boeing Alert
Requirements Bulletin. The missed airplanes are associated with the
service information mandated by AD 2013-08-18, Amendment 39-17435 (78
FR 25377, May 1, 2013). Those airplanes had the FiP gasket incorporated
in production, but a fluid leak test was not required as part of AD
2013-08-18 and its associated service information. Since the same non-
conformance may have been introduced in production on those airplanes,
the FAA concluded those airplanes must be included in the applicability
of this AD.
Further, after issuance of the NPRM, Boeing issued Boeing Alert
Requirements Bulletin 737-57A1359 RB, Revision 1, dated June 25, 2026
(Revision 1 of the Boeing Alert Requirements Bulletin), to include the
additional airplane serial numbers referenced in the applicability of
the proposed AD. Therefore, the FAA has updated paragraph (c) of this
AD to reference Revision 1 of the Boeing Alert Requirements Bulletin.
Request To Remove Exceptions to Service Information Instructions
American requested that the FAA remove the exceptions in paragraphs
(h)(2), (3), and (4) from the proposed AD and instead adopt the
instructions in the compliance tables and appendices of the original
issue of the Boeing Alert Requirements Bulletin. American stated that
the language in the service information sufficiently defines the
corrective action, and that retaining this information helps maintain
consistency and minimizes the potential for misinterpretation.
The FAA notes that the exception in paragraph (h)(2) is necessary
because the ``on-condition corrective action(s)'' specified in tables 1
and 2 of the Compliance and Accomplishment Instructions of the original
issue of the Boeing Alert Requirements Bulletin are not defined in that
bulletin. Similarly, the exceptions in paragraphs (h)(3) and (4) are
necessary because Appendices A and B of the original issue of the
Boeing Alert Requirements Bulletin do not explicitly specify to replace
the FiP gasket if any leak is found during the fluid leak test.
However, the FAA reviewed Revision 1 of the Boeing Alert Requirements
Bulletin and determined that Revision 1 negates the need for the
exceptions in paragraphs (h)(2), (3), and (4) of the proposed AD.
Therefore, the FAA has revised paragraph (g) of this AD to require
accomplishing all the applicable actions in Revision 1 of the Boeing
Alert Requirements Bulletin. Additionally, the FAA has added paragraph
(i) to this AD to provide credit for accomplishing the actions in
paragraph (g) of this AD before the effective date of this AD using the
original issue of the Boeing Alert Requirements Bulletin, except as
provided by the exceptions in paragraphs (i)(1) through (3) of this AD.
Request To Clarify Post-AD Requirements
Southwest asked if the FAA agrees that, after completing the
actions required by this AD, an alternative method of compliance (AMOC)
is not required to maintain the airplane per the Boeing aircraft
maintenance manual (AMM). Southwest stated a certain task in the Boeing
AMM provides instructions that vary subtly from the procedures in
Boeing Alert Requirements Bulletin 737-57A1359 RB.
[[Page 67450]]
The FAA agrees that an AMOC is not needed to maintain the airplane
after complying with the requirements of this AD if the airplane is
maintained per the Boeing AMM. The FAA notes that the unsafe condition
was introduced during airplane production through the application of
non-permitted sealant after the initial FiP gasket had cured. Since the
FAA has not received any reports of in-service events where anomalies
were introduced during maintenance based on AMM instructions, the FAA
considers the relevant AMM tasks to be appropriate. Further, Boeing has
updated the AMM task to include notes to prevent sealant touch-up after
the initial sealant application. Boeing has also updated the AMM
procedures for the fluid leak test to match the procedures in the
required service information. Those updates in the AMM instructions are
expected to support operators for improved maintenance of the FiP
gasket installed at the engine fuel shutoff valve access panel.
Conclusion
The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for minor editorial changes, this
AD is adopted as proposed in the NPRM. None of the changes will
increase the economic burden on any operator.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 737-57A1359 RB,
Revision 1, dated June 25, 2026. This material specifies procedures for
a detailed inspection of the FiP gasket at the engine fuel shutoff
valve access panel of the left- and right-side wing for correct sealant
installation, a fluid leak test of the engine fuel shutoff valve access
panels for any leak, and applicable on-condition actions. On-condition
actions include replacing the FiP gasket, repairing any leaks, and
repeating the leak test until no leak is found.
This material is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section.
Costs of Compliance
The FAA estimates that this AD affects 1,030 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:
Estimated Costs
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Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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Inspection.............................. 1 work-hour x $85 per hour = $0 $85 $87,550
$85.
Leak test............................... 1 work-hour x $85 per hour = 0 85 87,550
$85.
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The FAA estimates the following costs to do any necessary
replacements that would be required based on the results of the
inspection. The agency has no way of determining the number of aircraft
that might need these replacements:
On-Condition Costs
----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product
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Replacement............................. 2 work-hours x $85 per hour Negligible................. $170.
= $170.
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The FAA has received no definitive data on which to base the cost
estimates for the on-condition repairs specified in this AD.
The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this AD may be covered under warranty, thereby reducing the cost impact
on affected operators.
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.
Regulatory Findings
This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect on the States,
on the relationship between the national government and the States, or
on the distribution of power and responsibilities among the various
levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
The Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:
[[Page 67451]]
PART 39--AIRWORTHINESS DIRECTIVES
0
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
0
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive:
2026-21-08 The Boeing Company: Amendment 39-23497; Docket No. FAA-
2026-2725; Project Identifier AD-2025-00999-T.
(a) Effective Date
This airworthiness directive (AD) is effective December 1, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to The Boeing Company Model 737-700, -700C, -
800, and -900ER series airplanes, certificated in any category, as
identified in Boeing Alert Requirements Bulletin 737-57A1359 RB,
Revision 1, dated June 25, 2026.
(d) Subject
Air Transport Association (ATA) of America Code 57, Wings.
(e) Unsafe Condition
This AD was prompted by a leak through the form-in-place (FiP)
gasket at the engine fuel shutoff valve access panel found during a
leak check. An investigation found that the fairing requirements of
the engine fuel shutoff valve access panel caused thin regions of
the FiP gasket, which caused non-permitted sealant to be applied
after the initial FiP gasket had cured, resulting in an uneven
sealing surface on the engine fuel shutoff valve access panel and
leak. The FAA is issuing this AD to address incorrect or missing
sealant installation. The unsafe condition, if not addressed, could
result in fuel leaking onto the engine exhaust nozzle and a possible
fire on the ground.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
Except as specified by paragraph (h) of this AD: At the
applicable times specified in the ``Compliance'' paragraph of Boeing
Alert Requirements Bulletin 737-57A1359 RB, Revision 1, dated June
25, 2026, do all applicable actions identified in, and in accordance
with, the Accomplishment Instructions of Boeing Alert Requirements
Bulletin 737-57A1359 RB, Revision 1, dated June 25, 2026.
Note 1 to paragraph (g): Guidance for accomplishing the actions
required by this AD can be found in Boeing Alert Service Bulletin
737-57A1359, Revision 1, dated June 25, 2026, which is referred to
in Boeing Alert Requirements Bulletin 737-57A1359 RB, Revision 1,
dated June 25, 2026.
(h) Exceptions to Requirements Bulletin Specifications
Where the Compliance Time columns of the tables in the
``Compliance'' paragraph of Boeing Alert Requirements Bulletin 737-
57A1359 RB, Revision 1, dated June 25, 2026, refer to the original
issue date of Requirements Bulletin 737-57A1359 RB, this AD requires
using the effective date of this AD.
(i) Credit for Previous Actions
This paragraph provides credit for the actions specified in
paragraph (g) of this AD, if those actions were performed before the
effective date of this AD using Boeing Alert Requirements Bulletin
737-57A1359 RB, dated October 3, 2025, except as specified by
paragraphs (i)(1) through (3) of this AD:
(1) Where Table 1 and Table 2 in the Compliance and
Accomplishment Instructions paragraphs of Boeing Alert Requirements
Bulletin 737-57A1359 RB, dated October 3, 2025, specifies ``Do a
fluid leak test of the engine fuel shutoff valve access panel for
any leak. If any leak is found, do all applicable on-condition
corrective action(s) and repeat the leak test until no leak is
found'', this AD requires replacing that text with ``Do a fluid leak
test of the engine fuel shutoff valve access panel for any leak. If
any leak is found, replace the FiP gasket and repeat the leak test
until no leak is found''.
(2) Where step 4.b. of Appendix A in Boeing Alert Requirements
Bulletin 737-57A1359 RB, dated October 3, 2025, specifies ``If any
water leaks from the engine fuel shutoff valve access panel in less
than two minutes, the fluid leak test has failed'', this AD requires
replacing that text with ``If any water leaks from the engine fuel
shutoff valve access panel in less than two minutes, the fluid leak
test has failed. Replace the FiP gasket in accordance with Figure 3
and repeat the leak test until no leak is found''.
(3) Where step 4.b. of Appendix B in Boeing Alert Requirements
Bulletin 737-57A1359 RB, dated October 3, 2025, specifies ``If any
water leaks from the engine fuel shutoff valve access panel in less
than two minutes, the fluid leak test has failed'', this AD requires
replacing that text with ``If any water leaks from the engine fuel
shutoff valve access panel in less than two minutes, the fluid leak
test has failed. Replace the FiP gasket in accordance with Figure 4
and repeat the leak test until no leak is found''.
(j) Alternative Methods of Compliance (AMOCs)
(1) The Manager, AIR-520, Continued Operational Safety Branch,
FAA, has the authority to approve AMOCs for this AD, if requested
using the procedures found in 14 CFR 39.19. In accordance with 14
CFR 39.19, send your request to your principal inspector or
responsible Flight Standards Office, as appropriate. If sending
information directly to the manager of the Continued Operational
Safety Branch, send it to the attention of the person identified in
paragraph (k)(1) of this AD. Information may be emailed to:
<a href="/cdn-cgi/l/email-protection#43020e0c00032522226d242c35"><span class="__cf_email__" data-cfemail="a5e4e8eae6e5c3c4c48bc2cad3">[email protected]</span></a>. Before using any approved AMOC, notify your
appropriate principal inspector, or lacking a principal inspector,
the manager of the responsible Flight Standards Office.
(2) An AMOC that provides an acceptable level of safety may be
used for any repair, modification, or alteration required by this AD
if it is approved by The Boeing Company Organization Designation
Authorization (ODA) that has been authorized by the Manager, AIR-
520, Continued Operational Safety Branch, FAA, to make those
findings. To be approved, the repair method, modification deviation,
or alteration deviation must meet the certification basis of the
airplane, and the approval must specifically refer to this AD.
(k) Additional Information
(1) For more information about this AD, contact Erica Bayles,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; phone: 907-271-5844; email: <a href="/cdn-cgi/l/email-protection#0366716a60622d662d61627a6f6670436562622d646c75"><span class="__cf_email__" data-cfemail="92f7e0fbf1f3bcf7bcf0f3ebfef7e1d2f4f3f3bcf5fde4">[email protected]</span></a>.
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (l)(3)
of this AD.
(l) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference of the material listed in this paragraph
under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions
required by this AD, unless the AD specifies otherwise.
(i) Boeing Alert Requirements Bulletin 737-57A1359 RB, Revision
1, dated June 25, 2026.
(ii) [Reserved]
(3) For Boeing material identified in this AD, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; website <a href="http://myboeingfleet.com">myboeingfleet.com</a>.
(4) You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St.,
Des Moines, WA. For information on the availability of this material
at the FAA, call 206-231-3195.
(5) You may view this material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit <a href="http://www.archives.gov/federal-register/cfr/ibr-locations">www.archives.gov/federal-register/cfr/ibr-locations</a> or email <a href="/cdn-cgi/l/email-protection#274155094e4954574244534e4849674946554609404851"><span class="__cf_email__" data-cfemail="c8aebae6a1a6bbb8adabbca1a7a688a6a9baa9e6afa7be">[email protected]</span></a>.
Issued on October 20, 2026.
Lona C. Saccomando,
Acting Deputy Director, Integrated Certificate Management Division,
Aircraft Certification Service.
[FR Doc. 2026-21862 Filed 10-26-26; 8:45 am]
BILLING CODE 4910-13-P
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