The union of pilots at American Airlines has urged its members to exercise caution amid a "significant increase" in safety and maintenance issues within the airline, according to Bloomberg News on Monday.

The Allied Pilots Association cited "troublesome incidents" in a memo sent on April 13, including cases of leaving tools like a hammer inside the wheel well and a rise in collision incidents between aircraft during towing.

The association, which represents about 15,000 pilots, urged members to avoid rushing while performing their duties and not to succumb to pressure to do anything unsafe.

American Airlines did not immediately comment on the news.

It is noted that the company's shares declined by 1.3% at 1:25 PM in New York Stock Exchange trading.

It is also noted that the company's stock has dropped by 4.3% this year up to April 12.