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 all The Boeing Company Model 757-300 series airplanes. The NPRM was published in the Federal Register on April 2, 2026 (91 FR 16593). The NPRM was prompted by a report that crack growth analysis indicated that existing MPD and SSIP tasks do not provide adequate inspection opportunities to detect cracks in the upper frames around the uppermost fastener common to the fail-safe chord at the fuselage frame splices between stringers S-13 to S-14, from station (STA) 1380 to STA 1620. In the NPRM, the FAA proposed to require an inspection or maintenance record check for existing repairs, repetitive inspections of the upper frames around the uppermost fastener common to the fail-safe chord at the fuselage frame splices for any cracks, and applicable on-condition actions. The FAA is issuing this AD to address cracking in the upper frames around the uppermost fastener common to the fail-safe chord at certain fuselage frame splices, which could lead to multiple upper frame failures. The unsafe condition, if not addressed, could result in the inability of a principal structural element to sustain limit loads and the loss of continued safe flight and landing.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from Boeing who supported the NPRM without change.

The FAA received additional comments from Aviation Partners Boeing (APB) and United Airlines (United). The following presents the comments received on the NPRM and the FAA's response to each comment.

Effect of Winglets on Accomplishment of the Proposed Actions

APB stated that accomplishing Supplemental Type Certificate (STC) ST01518SE does not affect the actions specified in the proposed AD. APB stated that Boeing has delegation from APB to review and approve data in areas affected by STC ST01518SE for the blended winglet configuration. The provisions of paragraph (i)(2) in the proposed AD remain applicable to The Boeing Company Model 757-300 series airplanes modified by STC ST01518SE, with blended winglets or production wingtips installed.

The FAA concurs with the commenter. The FAA has redesignated paragraph (c) of the proposed AD as paragraph (c)(1) of this AD and added paragraph (c)(2) to this AD to state that installation of STC ST01518SE does not affect the ability to accomplish the actions required by this AD. Therefore, ( printed page 62300) for airplanes on which STC ST01518SE is installed, a “change in product” alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17.

Request To Correct Typographical Error in Service Material

United requested that the FAA revise Table 2 of Boeing Alert Requirements Bulletin 757-53A0122 RB, dated September 26, 2025, to correct the references to stringers S-13L and S-14L in certain steps. United stated that Table 2 applies to the right side in both the compliance and actions required for compliance sections and, therefore, the stringer references should be S-13R and S-14R.

The FAA agrees that Table 2 of Boeing Alert Requirements Bulletin 757-53A0122 RB, dated September 26, 2025, contains typographical errors in certain stringer references. The FAA has added an exception in paragraph (h)(3) of this AD to correct the typographical errors.

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 757-53A0122 RB, dated September 26, 2025. This material specifies procedures for performing a general visual inspection or a maintenance records check of the forward and aft sides of the upper frames at the frame splices between S-13 and S-14 on the left and right sides, from STA 1380 to STA 1620, for any repair and applicable on-condition actions. On-condition actions include contacting Boeing for alternative inspection and corrective action instructions and doing the alternative inspection and applicable corrective actions in the repaired areas.

This material also specifies procedures for repetitive detailed inspections of the upper frames around the uppermost fastener common to the fail-safe chord at the frame splices between S-13 and S-14 on the left and right sides, from STA 1380 to STA 1620, for any crack and applicable on-condition actions. On-condition actions include 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.

Costs of Compliance

The FAA estimates that this AD affects 37 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

The FAA has received no definitive data on which to base the cost estimates for the alternative inspections and on-condition actions 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: