The union also says it has seen incidents in which tools were left in wheel wells and items were left in the sterile area around planes parked at airport gates.

A spokesman said Monday that union officials have raised their concerns with senior managers at the airline and were encouraged by the company’s response.

American, which is based in Fort Worth, Texas, said it has an industry-leading safety management system. An airline spokesperson said American is in regular contact with regulators and unions “to further bolster our strong safety record and enhance our ever-evolving safety culture.”

Dennis Tajer, a pilot and spokesman for the union, said the union spoke recently with senior management, “and management’s initial response to our request was encouraging. We fully intend to do everything we can to assure that American maintains strong margins of safety.”

The Federal Aviation Administration declined to comment directly on the union’s allegations or whether the agency has increased its oversight of American as a result. In a statement, an FAA spokesperson said airlines required to have systems for identifying potential hazards before they become serious problems.

The safety committee of the Allied Pilots Association said in an email to members Saturday that the union “has been tracking a significant spike in safety- and maintenance-related problems in our operation.”

The union said American has increased the time between routine inspections on planes. It also said American has ended overnight maintenance checks unless a plane is written up for special attention or due for scheduled maintenance and now does “abbreviated” test flights on planes returning to service after major maintenance checks or long-term storage.

The union asked its members to report any safety or maintenance problems.

“We all understand that aviation accidents are the result of a chain of events — often a series of errors — and catching just one of those errors could prevent a tragedy,” the union said in the email.