FAA Proposes AD 2026-00409 for Boeing 737 Wing Skin Crack Inspections

The Federal Aviation Administration has issued a proposed Airworthiness Directive (AD 2026-00409) affecting all Boeing 737-700, -700C, -800, -900, and -900ER series aircraft. The directive addresses potential cracks in the outboard lower wing skin that could compromise structural integrity.

What Triggered This AD

During routine maintenance inspections, cracks were discovered in the outboard lower wing skin at the outboard end of stringer S-9, specifically at the most outboard fastener location. The FAA determined that this condition, if left unaddressed, could lead to the inability of the principal structural element to sustain limit loads, resulting in potential loss of structural integrity.

Affected Aircraft

This proposed AD affects a significant portion of the 737 Next Generation fleet:

Boeing 737-700 (all variants)
Boeing 737-700C (convertible)
Boeing 737-800 (all variants)
Boeing 737-900 (all variants)
Boeing 737-900ER (Extended Range)

The FAA estimates approximately 1,857 airplanes of U.S. registry are affected by this directive.

Required Actions

If adopted as proposed, the AD would require operators to:

Conduct inspections of the outboard lower wing skin on both left and right wings
Check for any existing repairs in the affected areas
Perform repetitive inspections for cracking at stringer S-9 and S-10 locations
Complete applicable on-condition actions if cracks are found

Compliance Timeline

The proposed AD is currently in the comment period, with comments due by February 26, 2026. Operators should monitor the Federal Register for the final rule, which will specify exact compliance deadlines once adopted.

Reference Documents

The following Boeing service documents relate to this AD:

Boeing Alert Requirements Bulletin 737-57A1356 RB (dated May 14, 2025)
Service Bulletin AP737-57-022, Revision 2 (dated August 27, 2025)

These documents are available through Boeing's online service portal or at regulations.gov under Docket No. FAA-2026-0010.

Impact on Operators

Given the widespread use of the 737NG family in commercial and cargo operations, operators should:

Review current maintenance schedules to identify opportunities for inspection
Coordinate with maintenance providers to ensure capacity for inspections
Monitor the rulemaking process for final compliance requirements
Budget for potential repairs if cracks are discovered during inspection

Submit Comments

Industry stakeholders can submit comments on this proposed AD through:

Online: regulations.gov (Docket No. FAA-2026-0010)
Mail: Docket Management Facility, U.S. Department of Transportation

Comments must be received by February 26, 2026.

FAA Contact

For technical questions about this AD, contact:

Owen Bley-Male FAA, 2200 South 216th St., Des Moines, WA 98198 Phone: 206-231-3992 Email: owen.f.bley-male@faa.gov

Finding Qualified Maintenance

Need to schedule wing inspections for your 737 fleet? Use Find Aircraft Maintenance to locate FAA-certified repair stations with Boeing 737 experience in your area. Filter by capabilities to find shops equipped for structural inspections and repairs.

Sources: Federal Register AD 2026-00409, Justia Regulation Tracker