NEW YORK (AP) — FedEx Express pilots voted overwhelmingly to authorize a strike in a move they hope will help their union win a new contract that would include pay raises.

The Air Line Pilots Association said Wednesday that 99% of its FedEx members who took part voted to authorize a strike, and turnout was 97%.

Federal law prohibits airline unions from conducting strikes until U.S. mediators have declared negotiations at an impasse — which has not happened at FedEx — and even then, Congress and the president can block a walkout.

Unions, however, believe that the votes increase their leverage at the bargaining table. The pilots' union and Memphis, Tennessee-based FedEx have been negotiating for two years over a new contract while terms of the previous one remain in effect.

"Our goal is to reach an agreement, not to strike," said Chris Norman, head of the union's FedEx chapter.

FedEx said the pilots' vote will not affect company operations and that it is focused on reaching an agreement with pilots "that is fair to them, our other team members, and all other FedEx stakeholders."

Pilots at Southwest Airlines and American Airlines recently voted to authorize strikes, and Delta Air Lines pilots did the same before reaching a contract that raised average pay 34% over four years.