Boeing has been advised of mandatory inspections for the 737 Next Generation aircraft, specifically in relation to horizontal stabilizer components. This comes after reports of looseness and excessive freepay causing pitch control issues. The order was publicized on January 9 and has requested comments from Boeing no later than February 23.
Under the order, Boeing would mandate inspections of both the left and right horizontal stabilizer pivot hinges, alongside the jackscrew, to understand the total freeplay value. This specifically relates to the Boeing 737-600, -700, 700C, -800, -900, and -900ER series of airplanes.
No Current Inspection Requirement
Currently, no set inspection requirement focuses on the wear and tear of horizontal stabilizer pivot hinges or the jackscrew, as per to the draft directive. However, the horizontal stabilizer freeplay has been directly linked to several reports that saw ‘pitch oscillation’ events, alerting the FAA and Boeing of this issue back in June last year.
Boeing has since alerted operators of the issue in a June 2025 bulletin, recommending inspections be undertaken. This most recent mandate by the FAA has been widely based on this earlier bulletin. While the draft directive is not specific to any one in-flight incident, it relies on airlines referring to the bulletin for more detailed inspection timetable details. The FAA directive summary below:
The FAA proposes to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This proposed AD was prompted by reports from multiple operators of pitch oscillations events due to excessive horizontal stabilizer freeplay. This proposed AD would require measuring the freeplay of the horizontal stabilizer pivot hinges and the jackscrew, and applicable on-condition actions. The FAA is proposing this AD to address the unsafe condition on these products.
Global Adoption Likely
While it is affecting the wider population of the 737 NG family of aircraft, the FAA mandate would apply to almost 2,000 U.S.-registered aircraft. It is widely expected that global adoption would follow. Looking at data from ch-aviation, it identifies that globally 5,165 active aircraft may be affected, operated by 206 international carriers.
Due to the pitch oscillation events, which are believed to be related to the horizontal stabilizer freeplay, if not addressed, could lead to a flutter event. A flutter event is dangerous, which is where an aircraft’s aerodynamic forces cause a positive feedback loop, which, as a result, causes vibrations, bending, and twisting, which can lead to a catastrophic failure. Such an event could lead to loss of control of the aircraft, endangering the lives of those onboard.
The FAA’s determination, as documents on the airworthiness directive, is that the unsafe condition described may likely exist or develop on other Boeing products of a similar design.
FAA Mandates Landing Gear Checks On Boeing 767s To Prevent Collapse
It applies to 574 US-registered B767s, which include 767-200s, 767-300s, and 767-300 Freighters.
Affected US Operators
In the United States, a number of key airlines may be affected by the directive, which includes American Airlines, Avelo Airlines, Delta, Fedex Express, Southwest Airlines, and 
United Airlines. A full list of the number of aircraft currently in operation is detailed in the table below:
|
Airline |
Active 737-600 |
737-700 |
737-800 |
737-900 |
|---|---|---|---|---|
|
American Airlines |
– |
– |
303 |
– |
|
Avelo Airlines |
– |
Eight |
12 |
– |
|
Delta Air Lines |
– |
– |
77 |
163 |
|
FedEx Express |
– |
– |
Eight |
– |
|
iAero Airways |
– |
– |
14 |
– |
|
Janet Airlines |
Six |
– |
– |
– |
|
Kalitta Charters |
– |
– |
Two |
– |
|
Northern Air Cargo |
– |
– |
One |
– |
|
Southern Air |
– |
– |
Eight |
– |
|
Southwest Airlines |
– |
400 |
207 |
– |
|
Sun Country Airlines |
– |
– |
54 |
– |
|
United Airlines |
– |
40 |
141 |
148 |
|
United States Air Force |
– |
12 |
– |
– |
|
United States Navy |
– |
17 |
– |
– |
Southwest Airlines remains the largest operator of the series, while American Airlines and United Airlines also have a large fleet of the planes. Outside of Europe, carriers such as Ryanair.
The cost of the proposed directive is estimated at six hours per aircraft, totalling $510 per plane (based on six hours at $85 per hour), amounting to a total of just over $1 million combined for all US airplanes.
