Proposed Rule2026-08154
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
April 27, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This proposed AD was prompted by reports of fuselage skin cracks found near the aft drain mast. This proposed AD would require inspection of the aft drain mast area and surrounding fuselage skin for any repair, repetitive inspections of the fuselage skin and structure common to the aft drain mast for any crack and any corrosion, and applicable on-condition actions. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 91 Issue 80 (Monday, April 27, 2026)</title>
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[Federal Register Volume 91, Number 80 (Monday, April 27, 2026)]
[Proposed Rules]
[Pages 22485-22487]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-08154]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-3868; Project Identifier AD-2025-01169-T]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and
-900ER series airplanes. This proposed AD was prompted by reports of
fuselage skin cracks found near the aft drain mast. This proposed AD
would require inspection of the aft drain mast area and surrounding
fuselage skin for any repair, repetitive inspections of the fuselage
skin and structure common to the aft drain mast for any crack and any
corrosion, and applicable on-condition actions. The FAA is proposing
this AD to address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by June 11,
2026.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://regulations.gov">regulations.gov</a>. Follow
the instructions for submitting comments.
<bullet> Fax: 202-493-2251.
<bullet> Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
<bullet> Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
AD Docket: You may examine the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2026-3868; 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 NPRM, any comments received, and other
information. The street address for Docket Operations is listed above.
Material Incorporated by Reference:
<bullet> For Boeing material identified in this proposed 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-2026-3868.
FOR FURTHER INFORMATION CONTACT: Luis Cortez-Muniz, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3958; email: <a href="/cdn-cgi/l/email-protection#bed2cbd7cd90df90ddd1cccadbc493d3cbd0d7c4fed8dfdf90d9d1c8"><span class="__cf_email__" data-cfemail="137f667a603d723d707c616776693e7e667d7a69537572723d747c65">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments using a method listed
under the ADDRESSES section. Include ``Docket No. FAA-2026-3868;
Project Identifier AD-2025-01169-T'' at the beginning of your comments.
The most helpful comments reference a specific portion of the proposal,
explain the reason for any recommended change, and include supporting
data. The FAA will consider all comments received by the closing date
and may amend this proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
<a href="http://regulations.gov">regulations.gov</a>, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.
Confidential Business Information
CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this NPRM contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this NPRM, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as ``PROPIN.'' The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this NPRM. Submissions containing CBI should be sent to Luis
Cortez-Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 206-231-3958; email: <a href="/cdn-cgi/l/email-protection#f29e879b81dc93dc919d80869788df9f879c9b88b2949393dc959d84"><span class="__cf_email__" data-cfemail="e08c958993ce81ce838f9294859acd8d958e899aa0868181ce878f96">[email protected]</span></a>. Any commentary that the FAA receives that is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.
Background
The FAA has received reports indicating cracks were found in the
fuselage skin underneath the aft drain mast on a Model 737-400
airplane. The FAA issued an NPRM that proposed to amend 14 CFR part 39
by adding an AD that would apply to certain Boeing Model 737-100, -200,
-200C, -300, -400, and -500 series airplanes. That NPRM was published
in the Federal Register on February 13, 2026 (91 FR 6798). During cross
model evaluation, Boeing determined that Model 737-600, -700, -700C, -
800, -900, and -900ER series airplanes could also be affected by the
unsafe condition due to configuration similarity; however, there have
been no reports of any cracking on these models. This condition, if not
addressed, could result in the inability of the principal structural
element (PSE) to sustain limit loads, which could result in rapid
decompression of the fuselage and the loss of structural integrity of
the airplane.
FAA's Determination
The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1421 RB,
dated March 20, 2025. This material specifies procedures for external
general visual inspection of the aft drain mast area and surrounding
fuselage skin for any repair; repetitive internal detailed inspection
of the aft drain mast fitting, surrounding fuselage skin, and structure
for any crack and any corrosion; repetitive external detailed
inspection of the fuselage skin common to the area
[[Page 22486]]
where the aft drain mast was removed for any crack and any corrosion;
external surface high frequency eddy current (HFEC) inspection on the
fuselage skin around the fastener holes and cutout for any crack; and
applicable on-condition actions. On-condition actions include
contacting Boeing for alternative inspections and corrective action
instructions, doing the alternative inspections and applicable on-
condition corrective actions, and contacting Boeing for repair
instructions and doing the repair.
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.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified
in the material already described, except for any differences
identified as exceptions in the regulatory text of this proposed AD.
For information on the procedures and compliance times, see this
material at <a href="http://regulations.gov">regulations.gov</a> under Docket No. FAA-2026-3868.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 1,987 airplanes of U.S. registry. The FAA estimates the
following costs to comply with this proposed AD:
Estimated Costs
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Cost on U.S.
Action Labor cost Parts cost Cost per product operators
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External general visual 14 work-hours x $85 $0 $1,190............. $2,364,530.
inspection. per hour = $1,190.
Detailed inspections and external 16 work-hours x $85 0 $1,360 per $2,702,320 per
surface HFEC inspection. per hour = Up to inspection cycle. inspection cycle.
$1,360 per
inspection cycle.
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The FAA has received no definitive data on which to base the cost
estimates for the alternative inspections and on-condition repairs
specified in this proposed AD.
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
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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 Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
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:
The Boeing Company: Docket No. FAA-2026-3868; Project Identifier AD-
2025-01169-T.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by June 11, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes, certificated in any
category.
(d) Subject
Air Transport Association (ATA) of America Code 53, Fuselage.
(e) Unsafe Condition
This AD was prompted by reports of fuselage skin cracks found
near the aft drain mast. The FAA is issuing this AD to address
cracking or corrosion in the fuselage skin or structure near the aft
drain mast. The unsafe condition, if not addressed, could result in
the inability of the principal structural element (PSE) to sustain
limit loads, which could result in rapid decompression of the
fuselage and the loss of structural integrity of the airplane.
(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 737-53A1421 RB, dated March 20, 2025, do
all applicable actions identified in, and in accordance with, the
Accomplishment Instructions of Boeing Alert Requirements Bulletin
737-53A1421 RB, dated March 20, 2025.
Note 1 to paragraph (g): Guidance for accomplishing the actions
required by this AD can be found in Boeing Alert Service Bulletin
737-53A1421, dated March 20, 2025, which is referred to in Boeing
Alert Requirements Bulletin 737-53A1421 RB, dated March 20, 2025.
(h) Exceptions to Requirements Bulletin Specifications
(1) Where the Compliance Time column of the table in the
``Compliance'' paragraph of
[[Page 22487]]
Boeing Alert Requirements Bulletin 737-53A1421 RB, dated March 20,
2025, refers to the original issue date of Requirements Bulletin
737-53A1421 RB, this AD requires using the effective date of this
AD.
(2) Where Boeing Alert Requirements Bulletin 737-53A1421 RB,
dated March 20, 2025, specifies contacting Boeing for repair
instructions or for alternative inspections: This AD requires doing
the repair or doing the alternative inspections and applicable on-
condition actions using a method approved in accordance with the
procedures specified in paragraph (i) of this AD.
(i) 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 (j) of this AD. Information may be emailed to:
<a href="/cdn-cgi/l/email-protection#aaebe7e5e9eacccbcb84cdc5dc"><span class="__cf_email__" data-cfemail="bcfdf1f3fffcdadddd92dbd3ca">[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.
(j) Additional Information
(1) For more information about this AD, contact Luis Cortez-
Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 206-231-3958; email: <a href="/cdn-cgi/l/email-protection#5f332a362c713e713c302d2b3a2572322a3136251f393e3e71383029"><span class="__cf_email__" data-cfemail="1e726b776d307f307d716c6a7b6433736b7077645e787f7f30797168">[email protected]</span></a>.
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (k)(3)
of this AD.
(k) 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 737-53A1421 RB, dated
March 20, 2025.
(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#84e2f6aaedeaf7f4e1e7f0edebeac4eae5f6e5aae3ebf2"><span class="__cf_email__" data-cfemail="96f0e4b8fff8e5e6f3f5e2fff9f8d6f8f7e4f7b8f1f9e0">[email protected]</span></a>.
Issued on April 23, 2026.
Lona C. Saccomando,
Acting Deputy Director, Integrated Certificate Management Division,
Aircraft Certification Service.
[FR Doc. 2026-08154 Filed 4-24-26; 8:45 am]
BILLING CODE 4910-13-P
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