The union for American Airlines Group Inc. pilots warned members to be vigilant amid a “significant spike” in safety- and maintenance-related problems at the carrier.

The Allied Pilots Association cited “problematic trends” in a memo sent April 13, including instances of tools like a hammer being left in airplane wheel wells and an increasing number of collisions between aircraft while they’re being towed. The union, which represents about 15,000 pilots, implored its members to avoid rushing while doing their jobs and to not be pressured into doing anything unsafe.

American didn’t immediately comment. Shares of the carrier fell 1.3% at 1:25 p.m. April 15 in New York trading. The stock had slid 4.3% this year through April 12.

The union message underscores the heightened scrutiny on airline safety following a January incident in which a panel blew off the side of an Alaska Airlines plane mid-flight. United Airlines Holdings Inc., in particular, has garnered unwanted attention over a series of headline-grabbing mishaps, including a wheel falling from a plane after takeoff and an aircraft skidding off an airport runway.

“While United Airlines is currently under public and government scrutiny, it could just as easily be American Airlines,” the APA said in its memo. 

The union recently spoke with senior management at the carrier about becoming involved earlier in assessments of safety risks and the “initial response to our request was encouraging,” said Dennis Tajer, a union spokesman. “We fully intend to do everything we can to assure that American maintains strong margins of safety.”

The union cited other problems, such as increasing instances of equipment being left in sterile areas where planes pull into gates and faulty paperwork documenting when damaged aircraft are ferried to another location.

APA also warned members to watch for hazards “while operating on the ramps and taxiways in congested airports staffed with inexperienced controllers and ground personnel.”

The Federal Aviation Administration (FAA) recently increased its oversight of United as part of a broad safety review, delaying some activities including the postponement of two new routes the airline had planned to begin in summer of 2024. The carrier is conducting its own internal review, as well.

Boeing Co.’s manufacturing and quality practices also have been under intense FAA scrutiny since the Alaska Airlines incident involving a nearly new 737 Max 9. The harsh spotlight now extends to the 787 Dreamliner, after an engineer at the planemaker alleged the company took manufacturing shortcuts on the aircraft to ease production bottlenecks.