FAA Orders Mandatory Inspections on Boeing 787s After Wing 'Shim Gap' Defects Found
The U.S. Federal Aviation Administration has finalized a new airworthiness directive ordering operators of certain Boeing 787 Dreamliners to carry out repetitive inspections of wing structure, after Boeing's own investigation found that manufacturing gaps at critical joints exceeded approved engineering tolerances. The directive, published Wednesday, August 26, closes out a process that began with a Boeing bulletin a year earlier and a proposed rule from the FAA in March.
What the FAA found
The final directive covers certain Boeing 787-8, 787-9 and 787-10 airplanes and stems from an investigation Boeing conducted into manufacturing errors involving the lower side-of-body splice plates, which connect the fuselage to the lower outboard wing skins. According to the FAA, Boeing determined that gaps requiring shims — thin filler pieces used to close small mismatches between structural parts during assembly — may have exceeded the tolerances allowed under the jet's FAA-approved design and production specifications.
Those specifications call for fuselage gaps at these joints not to exceed five thousandths of an inch, or about 0.12 millimeters, according to reporting on Boeing's engineering standards. When gaps run wider than that, mechanics assembling the aircraft may need to apply high "pull-up" forces to draw the components together and close the joint before fastening. Boeing's investigation concluded that this force could create the conditions for fatigue cracks to form around fastener holes over time.
Left unaddressed, the FAA and Boeing say, undetected fatigue cracks could continue to grow and eventually weaken the wing's primary structure to the point where it could no longer sustain its design limit load — potentially compromising the airplane's continued safe flight and landing. The FAA's directive language uses that standard formulation, common to structural airworthiness directives, without asserting that any in-service failure has occurred.
What operators must now do
The directive requires, depending on the specific aircraft's configuration and prior inspection or repair history, a mix of:
- Repetitive ultrasonic inspections at certain splice plates, rear spar terminal fittings, lower chords, front spar terminal fittings and jack pads, to check for cracks that cannot be seen with the naked eye
- Repetitive detailed visual inspections of certain splice plates for surface cracks
- Applicable "on-condition" corrective actions — meaning repair or further inspection is triggered if a crack is found
Because the inspections are repetitive rather than one-time checks, affected aircraft will need to be rechecked at set intervals for the remainder of their service life unless a permanent terminating repair is applied.
How the issue was discovered
Boeing has been dealing with a series of 787 manufacturing-quality issues tied to gaps and shimming at structural joints for several years, following whistleblower complaints and FAA scrutiny of the program's quality-control processes. According to reporting on FAA internal communications, out-of-tolerance gaps have separately been identified at fuselage section joins, at a forward pressure bulkhead, and in structure surrounding passenger and cargo doors — with gap-related manufacturing defects believed to be present in more than 1,000 Dreamliners built to date, across the wider set of issues Boeing has disclosed to regulators over time.
The wing splice plate issue specifically addressed in this week's directive was first flagged by Boeing in an Alert Requirements Bulletin issued in August 2025. The FAA proposed making the associated inspections mandatory in March 2026, and after a public comment period, finalized the rule this week.
Context: a program still under the microscope
The 787 has been one of Boeing's most commercially successful widebody programs, but its production system has faced repeated FAA and congressional scrutiny since 2020, when the manufacturer voluntarily paused deliveries for over a year to work through gap and shimming defects across the fuselage. Boeing has said its data shows the fleet remains structurally sound and that the defects identified do not represent an immediate safety-of-flight issue for aircraft currently in service, which is why the FAA's remedy in cases like this is scheduled inspection rather than an immediate grounding.
Airlines operating 787s — including major U.S. and international widebody carriers — will need to fold the new ultrasonic and detailed visual checks into their maintenance schedules within the compliance windows set out in the directive. The FAA typically sets initial compliance thresholds based on aircraft accumulated flight cycles or time in service, with repetitive intervals following.
Boeing has not indicated the wing splice plate issue will affect delivery rates for new-build 787s, which have been a bright spot for the company's production recovery in 2026 as it works to close the delivery gap with Airbus.
What happens next
The FAA directive is now final and legally binding on U.S.-registered aircraft; other civil aviation authorities that recognize FAA airworthiness directives, including regulators overseeing many international 787 operators, are expected to mirror the requirement or issue parallel directives of their own, as is standard practice for widebody structural issues originating with a U.S.-certificated manufacturer.
No in-service failure or accident has been linked to the shim gap issue. This report reflects verified reporting on the FAA's published rule and Boeing's own investigation findings as described in that rule; further technical detail, including exact compliance timelines by aircraft configuration, is contained in the full Federal Register notice.
Sources
- FAA Requires Inspections of Some Boeing 787 Dreamliners for Gaps — Bloomberg
- FAA To Mandate Boeing 787 Inspections Following 'Shim Gap' Manufacturing Errors — Simple Flying
- Airworthiness Directives; The Boeing Company Airplanes — Federal Register
- FAA to Mandate Further Boeing 787 Structural Inspection — International Federation of Airworthiness
- FAA Proposes New 787 Inspection Mandate: 'Shim Gaps' — Aero-News Network