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 Boeing Model 737-8, 737-9, and 737-8200 airplanes. The NPRM was published in the Federal Register on November 25, 2025 (90 FR 53243). The NPRM was prompted by reports indicating that cracking was found in the bear strap and stub frame at the forward galley door cutout, from station (STA) 290 to STA 296 and between stringer S-8R and stringer S-9R. In the NPRM, the FAA proposed to require inspections for existing repairs; an inspection for any crack of the fuselage skin, bear strap, and stub frame; repetitive inspections for any crack of the bear strap and stub frame; and applicable on-condition actions. The FAA is issuing this AD to address any crack in the fuselage skin, bear strap, and stub frame at the forward galley door cutout from STA 290 to STA 296 and between stringer S-8R and stringer S-9R, before it reaches critical length. The unsafe condition, if not addressed, may result in the inability of a principal structural element to sustain limit load, which could adversely affect the structural integrity of the airplane.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from four commenters, including Boeing, The Foundation for Aviation Safety, 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 Explain How the Root Cause Is Addressed

The Foundation for Aviation Safety asked what the FAA and Boeing are doing to address the root cause of the defect. The commenter also asked if a structural defect is important enough to immediately ground an airplane after it is detected, why is the inspection for defects not accomplished long before the proposed compliance time.

The FAA is issuing this AD to address the unsafe condition on in-service airplanes. The required compliance times for the initial inspection and on-condition repetitive inspections and repair were established to ensure any crack is detected and repaired before the crack reaches critical length with multiple opportunities for detection. The rulemaking timeline was based on Boeing 737 fleet findings, supporting analysis, and the severity of the effect on the airplane ( i.e., safety consequences) if cracking propagates beyond a critical length. The FAA determined that the required actions and compliance times provide an acceptable level of safety. In addition, Boeing is introducing changes to the manufacturing process that address the root cause of the unsafe condition on in-production airplanes. The FAA did not change this AD as a result of this comment.

Request To Correct Typographical Error in Requirements Bulletin

Boeing, Southwest, and United requested that flag note (a) of Figure 6 in Boeing Alert Requirements Bulletin 737-53A1420 RB, dated February 13, 2025, be corrected to refer to inspection of the stub frame instead of inspection of the bear strap. The commenters noted that there is a typographical error which states “bear strap” instead of “stub frame” in flag note (a) of Figure 6 and requested the FAA revise the proposed AD to add an exception to correct the error.

The FAA agrees. The FAA has added an exception in paragraph (h)(3) of this AD accordingly.

Request To Use Later Approved Revisions of Referenced Drawings

United requested to use later approved revisions of the drawings referenced in the Work Instructions, Table 1, footnote (c) of Boeing Alert Requirements Bulletin 737-53A1420 RB, dated February 13, 2025, without obtaining an alternative method of compliance (AMOC). United noted that the Picture Sheet Data List (PSDL) referenced in the work instructions direct operators to use Boeing PSDL 141A8370 revision C and Boeing Module Parts List (MPL) 141A8370-11. United noted that this approach restricts operators from utilizing the most current, FAA-approved revisions of the applicable PSDL and MPL data that may be effective for the aircraft configuration.

The FAA disagrees. The FAA may not refer to any document that does not yet exist in an AD. The specific drawing revisions are required as they include prescriptive instructions for the stub frame replacement when damage is found common to the stub frame. To ensure the configuration maintains an acceptable level of safety, the service information does not currently allow for later approved revisions. However, if later approved revisions of the drawings provide an acceptable level of safety, operators may request approval of an AMOC under the provisions of paragraph (i) of this AD. The FAA did not change this AD as a result of this comment.

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, and any other changes described previously, 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 737-53A1420 RB, dated February 13, 2025. This material specifies procedures for doing Option 1 or Option 2 actions as specified below, and applicable on-condition actions. On-condition actions include replacing the stub frame, doing alternative inspections, and doing a repair.

• Option 1—Perform initial external general visual inspection (GVI) of the fuselage skin and gap cover for any repair, initial internal GVI of the bear strap and stub frame for any repair, and repetitive internal high frequency eddy current (HFEC) inspections of the bear strap and stub frame for any crack.
• Option 2—Perform initial external GVI of the fuselage skin and gap cover for any repair, initial internal GVI of the stub frame for any repair, initial external HFEC inspection of the fuselage skin for any crack, initial external low frequency eddy current (LFEC) inspection of the bear strap for any crack, initial internal HFEC inspection of the stub frame for any crack, and repetitive internal HFEC inspections of the bear strap and stub frame for any crack.

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 476 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: ( printed page 58811)

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 this replacement:

The FAA has received no definitive data that would enable the agency to provide cost estimates for the on-condition repairs specified in this 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

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.

The Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: