FAA Directive Covers 1,987 Boeing 737s, Requires Horizontal Stabilizer Clearance Inspection
Key Facts
The U.S. Federal Aviation Administration issued airworthiness directive AD 2026-20-14 for Boeing 737-600, -700, -700C, -800, -900 and -900ER aircraft, estimating that it covers 1,987 aircraft registered in the United States. The final directive was published on October 19, 2026, and takes effect on November 23. The measure requires an inspection of horizontal stabilizer clearance after operators reported incidents of aircraft pitch oscillation. The agency said excessive clearance that is not corrected could lead to stabilizer flutter, potentially resulting in loss of aircraft control. The directive makes measurement and, if necessary, repair part of the airworthiness requirements for the specified models.
The reports concern increased clearance in the horizontal stabilizer hinges and jackscrew mechanism, rather than identifying a single mechanism as the sole cause. The inspection measures clearance at the stabilizer pivot hinges and jackscrew, then determines the follow-up action based on the results. Conditional actions include remeasuring total stabilizer clearance, repeating the hinge and jackscrew measurements, and repairing or replacing worn parts. Compliance therefore does not end with an initial reading; the technical findings determine whether the aircraft needs additional work. The agency ties these steps to addressing excessive clearance before it develops into stabilizer flutter.
The FAA estimated that the initial measurement would take 6 work-hours per aircraft, at a cost of $510 per aircraft. For the 1,987 affected U.S. aircraft, the estimated total cost to operators is $1,013,370. The estimate excludes the cost of required spare parts, so actual expenses may vary for aircraft requiring repairs or parts replacement. The agency thus distinguishes the estimated inspection cost from any maintenance work that worn parts may require. The available materials did not provide a total estimate for those repairs or parts.
The FAA adopted the directive as proposed, with minor editorial changes that it said would not increase the economic burden on any operator. In considering comments, it rejected Canadian North’s request to extend the initial inspection threshold from 12 to 36 months after the date of Boeing’s original bulletin. It also rejected United Airlines’ request to lengthen repeat intervals for aircraft with replaced parts. The FAA said the specified compliance times maintain an acceptable level of safety for the fleet. It added that the repeat intervals were selected to prevent excessive clearance in original, new or replaced parts.
The regulatory process began with a proposed rule published by the FAA on January 9, 2026, followed by a correction published on January 16, with February 23, 2026, retained as the deadline for comments. On implementation of the inspection, the agency rejected Alaska Airlines’ proposal to amend the action schedule, but said operators may conduct a temporary inspection early and then complete repairs or replacement during the same maintenance period. An inspection is required after repairs and before the aircraft returns to service. The agency said operators may request an extension to a specified compliance deadline if they provide sufficient data showing that the new deadline would provide an acceptable level of safety. The final directive takes effect on November 23, 2026.