ARLINGTON- The Federal Aviation Administration (FAA) has ordered tail inspections on 1,987 US-registered Boeing 737 Next Generation (737NG) jets after operators reported their noses moving up and down mid-flight.
United Airlines (UA) and Alaska Airlines (AS) asked for changes to the rule. The FAA rejected the requests, and Airworthiness Directive (AD) 2026-20-14 takes effect on November 23, 2026.
FAA Mandates Freeplay Checks on 737NG Stabilizers
The final rule covers the Boeing 737-600, -700, -700C, -800, -900 and -900ER. The Boeing 737 MAX family is not affected. The FAA published the directive in the Federal Register on October 19, 2026. It adopted the rule as proposed, with only minor editorial changes.
Airlines must measure excessive movement, known as freeplay, at the left and right horizontal stabilizer pivot hinges and at the jackscrew. They must follow Boeing Alert Requirements Bulletin 737-55A1104 RB, dated June 12, 2025.
Depending on the results, operators must determine total stabilizer freeplay, repeat the measurements at set intervals, or repair or replace worn parts.
Winglets installed under Aviation Partners Boeing’s supplemental type certificate do not affect compliance.
Multiple operators reported pitch oscillation events caused by excessive stabilizer freeplay. The FAA did not disclose how many incidents occurred, when they happened, or which airlines were involved.
Stabilizer Wear Creates Risk
On the 737, the horizontal stabilizer moves to adjust the aircraft’s nose-up or nose-down position.
It pivots on two hinges, while a jackscrew moves it into position. As these parts wear, freeplay can increase. If it becomes excessive, the stabilizer may experience flutter. The FAA stated:
“The unsafe condition, if not addressed, could lead to a flutter event, which can result in loss of control of the airplane.”
Airlines Asked for More Time, and FAA Said No
The FAA first proposed the order on January 9, 2026. A correction followed on January 16. Four commenters, including Alaska Airlines, Canadian North and United Airlines, asked for changes.
United, which has more than 300 affected aircraft, asked for longer repeat-inspection intervals on aircraft with newly replaced parts, specifically hinge bearings. It also asked for credit for freeplay checks done under a 2022 Boeing multi-operator message.
The FAA said the intervals are meant to ensure excessive freeplay does not develop in either original or replacement parts. It added that credit was unnecessary because aircraft with accepted earlier checks already get some relief under the Boeing bulletin.
Alaska Airlines asked to repair or replace worn parts without doing interim freeplay checks. The FAA declined but said operators can do the interim check early and complete repairs in the same maintenance period.
A post-repair inspection must still confirm freeplay is within limits before the aircraft returns to service.
Canadian North asked to move the initial inspection deadline from 12 months to 36 months, so the work could coincide with heavy maintenance visits. The FAA declined. Operators can still request an Alternative Method of Compliance if they submit data showing an acceptable level of safety.
Inspection Costs and Labor Estimates
The FAA estimates each freeplay measurement will take 6 work hours. At $85 per hour, that costs $510 per aircraft, or $1,013,370 across the US fleet.
A repeat measurement carries the same $510 labor cost, and repairing or replacing worn parts is estimated at one work hour, or $85. The FAA has no definitive data on the cost of replacement parts.
Global 737NG Fleet and Previous Inspections
The directive currently covers US-registered aircraft only. Authorities in other countries will decide whether to mandate the same checks.
Data from ch-aviation shows more than 5,160 737NG aircraft listed as active worldwide. The 737-800 is the most common commercial jet model in service in the US today.
Southwest Airlines is the world’s largest Boeing 737 operator, with 803 aircraft across the 737 family as of June 30, 2026. Its filing lists 288 737-700s and 192 737-800s, a combined 480 NG aircraft.
Irish ultra-low-cost carrier Ryanair ranks second with more than 400 737NGs, followed by United and American Airlines.
Boeing delivered more than 7,000 737NGs between 1997 and January 2020, when the last jets were handed over.
The fleet has faced widespread inspections before. In 2019, cracks in the “pickle fork” structure connecting the wings to the fuselage led the FAA to order inspections on US-registered 737NGs. Dozens of aircraft were grounded worldwide.
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