[Federal Register Volume 91, Number 7 (Monday, January 12, 2026)]
[Proposed Rules]
[Pages 1104-1107]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-00409]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-0010; Project Identifier AD-2025-01181-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 737-700, -700C, -800, -900, and -900ER
series airplanes. This proposed AD was prompted by reports of cracks in
the outward lower wing skin at the outboard end of a certain stringer.
This proposed AD would require an inspection of the outboard lower wing
skin on the left and right wing for any repair, repetitive inspections
for cracking 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 February
26, 2026.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to regulations.gov. Follow
the instructions for submitting comments.
Fax: 202-493-2251.
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.
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 regulations.gov under
Docket No. FAA-2026-0010; or in person at Docket Operations between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD
docket
[[Page 1105]]
contains this NPRM, any comments received, and other information. The
street address for Docket Operations is listed above.
Material Incorporated by Reference:
For Aviation Partners Boeing material identified in this
proposed AD, contact Aviation Partners Boeing, 555 Andover Park West,
Suite 200, Tukwila WA 98188; telephone 206-830-7699; email:
[email protected]; website aviationpartnersboeing.com.
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 myboeingfleet.com.
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. Boeing Alert Requirements Bulletin 737-57A1356
RB, dated May 14, 2025, is also available at regulations.gov under
Docket No. FAA-2026-0010.
FOR FURTHER INFORMATION CONTACT: Owen Bley-Male, FAA, 2200 South 216th
St., Des Moines, WA 98198; phone: 206-231-3992; email: [email protected].
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-2026-0010;
Project Identifier AD-2025-01181-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
regulations.gov, 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 Owen
Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; email: [email protected]. 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 that during routine
maintenance inspections, cracks were found in the outboard lower wing
skin at the outboard end of stringer S-9, common to the most outboard
fastener. The cracks extended in the forward and aft direction and
ranged from 2 inches to 5 inches in length. The affected airplanes had
accumulated between 20,602 to 30,150 flight cycles and 41,777 to 77,993
flight hours at the time of finding. Further analysis determined that
stringer S-10 has an equivalent stress level to stringer S-9 and could
also be susceptible to early cracking. This condition, if not
addressed, could lead to the inability of the principal structural
element to sustain limit loads and subsequent 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 737-57A1356 RB,
dated May 14, 2025. This material specifies procedures for an external
general visual inspection of the outboard lower wing skin on the left
and right wings, at the two most outboard fasteners at S-9 and S-10,
for any repair; repetitive external surface high frequency eddy current
(HFEC) inspections for cracking at the outboard lower wing skin on the
left and right wings, at the two most outboard fasteners at S-9 and S-
10; and applicable on-condition actions. On-condition actions include
contacting Boeing for alternative inspections or repair instructions
and doing the alternative inspections if repairs are found or doing the
repair if cracks are found.
The FAA also reviewed Aviation Partners Boeing Alert Service
Bulletin AP737-57-022, Revision 2, dated August 27, 2025. This material
specifies procedures for an external general visual inspection of the
outboard lower wing skin on the left and right wings, at the two most
outboard fasteners at S-9 and S-10, for any repair; repetitive external
surface HFEC inspections for cracking at the outboard lower wing skin
on the left and right wings, at the two most outboard fasteners at S-9
and S-10; and applicable on-condition actions. On-condition actions
include contacting Aviation Partners Boeing for alternative inspections
or repair instructions and doing the alternative inspections if repairs
are found or doing the repair if cracks are found, and repair for any
crack outside of the boundary of the skin cutout. 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 Boeing
Alert Service Bulletin 737-57A1356, dated May 14, 2025, at
regulations.gov under Docket No. FAA-2026-0010.
The earliest initial compliance time for the actions in the
Aviation Partners Boeing Alert Service Bulletin AP737-57-022, Revision
2, dated August 27, 2025, is before 20,000 flight cycles or before
40,000 flight hours, whichever comes first.
The repetitive intervals vary depending on group configuration. The
earliest repetitive interval is 3,000 flight cycles.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 1,857 airplanes of U.S. registry. The FAA
[[Page 1106]]
estimates the following costs to comply with this proposed AD:
Estimated Costs
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Parts
Action Labor cost cost Cost per product Cost on U.S. operators
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General visual inspection (left and 2 work-hours x $85 per $0 $170.................................. $315,690.
right wing). hour = $170.
HFEC inspection...................... 2 work-hours x $85 per 0 $170 per inspection cycle............. $315,690 per inspection cycle.
hour = $170 per
inspection cycle.
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The FAA estimates the following costs to do any necessary repairs
for any crack outside the boundary of the skin cutout that would be
required based on the results of the proposed inspection specified in
Aviation Partners Boeing Alert Service Bulletin AP737-57-022, Revision
2, dated August 27, 2025. The agency has no way of determining the
number of aircraft that might need these on-condition actions:
On-Condition Costs
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Action Labor cost Parts cost Cost per product
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Repairs.......................... 54 work-hours x $85 Up to $11,180.............. Up to $15,770.
per hour = $4,590.
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The FAA has received no definitive data on which to base the cost
estimates for other on-condition repairs and alternative inspections
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-2026-0010; Project Identifier AD-
2025-01181-T.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by February 26, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all The Boeing Company Model 737-700, -700C,
-800, -900, and -900ER series airplanes, certificated in any
category.
(d) Subject
Air Transport Association (ATA) of America Code 57, Wing.
(e) Unsafe Condition
This AD was prompted by reports of cracks in the outward lower
wing skin at the outboard end of stringer S-9. The FAA is issuing
this AD to address cracks on the left and right wing at outboard
fasteners at S-9 and S-10. The unsafe condition, if not addressed,
could lead to the inability of the principal structural element to
sustain limit loads and subsequent loss of structural integrity of
the airplane.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
(1) For all airplanes except those identified in paragraph
(g)(2) of this AD: Except as specified by paragraphs (h)(1) and (2)
of this AD, at the applicable times specified in the ``Compliance''
paragraph of Boeing Alert Requirements Bulletin 737-57A1356 RB,
dated May 14, 2025, do all applicable actions identified in, and in
accordance with, the Accomplishment Instructions of Boeing Alert
Requirements Bulletin 737-57A1356 RB, dated May 14, 2025.
Note 1 to paragraph (g)(1): Guidance for accomplishing the
actions required by this AD can be found in Boeing Alert Service
Bulletin 737-57A1356, dated May 14, 2025, which is referred to in
Boeing Alert Requirements Bulletin 737-57A1356 RB, dated May 14,
2025.
(2) For all airplanes identified in Aviation Partners Boeing
Alert Service Bulletin AP737-57-022, Revision 2, dated August 27,
[[Page 1107]]
2025: Except as specified by paragraphs (h)(3) and (4) of this AD,
at the applicable times specified in paragraph 1.E., ``Compliance''
of Aviation Partners Boeing Alert Service Bulletin AP737-57-022,
Revision 2, dated August 27, 2025, do all applicable actions
identified in, and in accordance with, the Accomplishment
Instructions of Aviation Partners Boeing Alert Service Bulletin
AP737-57-022, Revision 2, dated August 27, 2025.
(h) Exceptions to Requirements Bulletin and Service Bulletin
Specifications
(1) Where the Compliance Time columns of the tables in the
``Compliance'' paragraph of Boeing Alert Requirements Bulletin 737-
57A1356 RB, dated May 14, 2025, refer to the original issue date of
Requirements Bulletin 737-57A1356 RB, this AD requires using the
effective date of this AD.
(2) Where Boeing Alert Requirements Bulletin 737-57A1356 RB,
dated May 14, 2025, specifies contacting Boeing for repair
instructions or for alternative inspections: This AD requires doing
the repair, and doing the alternative inspections and applicable on-
condition actions using a method approved in accordance with the
procedures specified in paragraph (j) of this AD.
(3) Where the Compliance Time columns of the tables in the
``Compliance'' paragraph of Aviation Partners Boeing Alert Service
Bulletin AP737-57-022, Revision 2, dated August 27, 2025, refer to
the original issue date of Service Bulletin AP737-57-022, this AD
requires using the effective date of this AD.
(4) Where Aviation Partners Boeing Alert Service Bulletin AP737-
57-022, Revision 2, dated August 27, 2025, specifies contacting
Aviation Partners Boeing for repair instructions or for alternative
inspections: This AD requires doing the repair, and doing the
alternative inspections and applicable on-condition actions using a
method approved in accordance with the procedures specified in
paragraph (j) of this AD.
(i) Credit for Previous Actions
This paragraph provides credit for the actions specified in
paragraph (g)(2) of this AD, if those actions were performed before
the effective date of this AD using Aviation Partners Boeing Alert
Service Bulletin AP737-57-022, dated April 17, 2025, or Aviation
Partners Boeing Alert Service Bulletin AP737-57-022, Revision 1,
dated June 13, 2025.
(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:
[email protected]. 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 Owen Bley-Male,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; email: [email protected].
(2) For Aviation Partners Boeing material identified in this AD
that is not incorporated by reference, contact Aviation Partners
Boeing, 555 Andover Park West, Suite 200, Tukwila, WA 98188;
telephone 206-830-7699; email: [email protected];
website aviationpartnersboeing.com.
(3) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (l)(4)
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) Aviation Partners Boeing Alert Service Bulletin AP737-57-
022, Revision 2, dated August 27, 2025.
(ii) Boeing Alert Requirements Bulletin 737-57A1356 RB, dated
May 14, 2025.
(3) For Aviation Partners Boeing material identified in this AD,
contact Aviation Partners Boeing, 555 Andover Park West, Suite 200,
Tukwila, WA 98188; telephone 206-830-7699; email:
[email protected]; website
aviationpartnersboeing.com.
(4) 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 myboeingfleet.com.
(5) 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.
(6) You may view this material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].
Issued on January 8, 2026.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2026-00409 Filed 1-9-26; 8:45 am]
BILLING CODE 4910-13-P