FedEx pilots have rejected a tentative contract deal with the parcel delivery firm and the two sides will reopen negotiations, likely under the supervision of the National Mediation Board, the company and the pilots' union said on Monday.

The Air Line Pilots Association (ALPA) did not detail the reasons for the rejection or the vote tally. FedEx said the pilot union's vote will "have no impact on our service."

FedEx shares were near flat in midday trading, down 0.4% to $258.69.

"Our members have spoken and we will now regroup," Captain Chris Norman, FedEx ALPA chair, said in a statement. The union represents 6,000 FedEx pilots.

The tentative FedEx deal included a 30% pay increase and a 30% increase to the pilots' legacy pensions.

Earlier this month United Airlines and its pilots - also represented by ALPA -- announced a tentative deal that included a cumulative pay increase of up to 40.2%.

American Airlines and the Allied Pilots Association are revising their tentative deal following the United agreement. Over the weekend, American Airlines pilots indefinitely postponed their ratification vote after the airline boosted its offer.

With fewer pilots and rebounding demand, U.S. unions have enjoyed enhanced bargaining power in negotiations during the part year.

(Reporting by Priyamvada C in Bengaluru and Lisa Baertlein in Los Angeles; Editing by Devika Syamnath and Susan Heavey)