More than 50 aircraft technicians and crew chiefs, responsible for maintaining aircraft flying 23 daily departures, will be balloted from 13-30 September.

The Unite union said engineers are “angry” about a three-year pay offer and warned industrial action would bring “massive disruption” to the carrier’s operations.

According to Unite, in the first year of the current pay offer, technicians would receive a 5.3% rise and crew chiefs 3.8%. In the second year, all workers would receive a lump sum cash payment, while in the third year a pay freeze would be implemented.

Unite highlighted how the real rate of inflation currently stood at 12.3%.

General secretary Sharon Graham said: “American Airlines’ pay offer is appalling. It amounts to a significant real terms year-by-year wage cut. Our members will no longer accept what are cuts in real wages as the cost of living crisis spirals.

Unite regional officer Joe McGowan added: “Any disruption caused to American Airlines’ Heathrow operations will be the airline’s own fault for putting forward such an unacceptable offer. These are highly skilled and committed workers, yet American Airlines has offered them what is in effect a three-year pay cut. It needs to go back to the drawing board and table a realistic proposal on pay.”