The US Federal Aviation Administration (FAA) has ordered inspections of nearly 2,000 Boeing 737 Next Generation aircraft after multiple operators reported pitch oscillations linked to excessive looseness in the horizontal stabilizer mechanism.
The airworthiness directive, published on October 19, 2026, requires operators to measure movement in the stabilizer’s pivot hinges and jackscrew, then carry out additional checks, repairs or parts replacements depending on the findings.
The FAA estimates that 1,987 US-registered aircraft are affected. The directive covers 737-600, -700, -700C, -800, -900 and -900ER aircraft. It does not apply to the 737 MAX.
The rule takes effect on November 23, 2026, with inspections due according to the compliance schedule incorporated into the directive.
The horizontal stabilizer is the movable horizontal surface on the aircraft’s tail that helps control its nose-up or nose-down attitude. Excessive movement within its supporting mechanism, known as freeplay, can allow unwanted motion.
The FAA said the reported pitch oscillations were caused by excessive stabilizer freeplay and warned that leaving the condition uncorrected could lead to flutter, a potentially dangerous vibration that can result in loss of control.
The final directive follows a proposed rule published in January 2026 and incorporates inspection procedures detailed in a Boeing bulletin from June 12, 2025.
Some airlines sought adjustments to the inspection requirements during the public comment period. Canadian North asked the FAA to extend the initial inspection threshold from 12 months to 36 months, arguing that the longer period would allow the work to coincide with heavy maintenance visits and give operators more time to arrange parts and labor.
United Airlines requested longer repeat inspection intervals for aircraft fitted with replacement hinge bearings, compared with those retaining their original parts.
The FAA rejected both requests. It said the inspection schedule was necessary to maintain an acceptable level of safety and that excessive freeplay needed to be monitored whether components were original, repaired or newly installed.
The agency said it would consider individual requests for extensions if operators supplied sufficient evidence that an alternative schedule would maintain safety.
The agency estimates that the freeplay measurement will require six work-hours per aircraft, costing $510 at its assumed labor rate of $85 an hour. Across the affected US fleet, that amounts to approximately $1 million.
Additional inspections and repairs would increase those costs. The FAA said it could not determine how many aircraft would need replacement components and did not have definitive prices for the worn parts that might require replacement.