Pilots of FedEx Express, a unit of FedEx Corp, have voted "overwhelmingly" in support of a strike, the Air Line Pilots Association (ALPA) said on Wednesday.

From the 99% of members who participated in the vote, 97% authorized union leaders to call a strike, if needed, to achieve a new contractual agreement with the delivery firm.

FedEx pilots are currently working under contractual provisions and benefits arrived at in 2015, and negotiations for a new agreement had begun in 2021.

"The ball is in the management's court, and it's time for the company to get serious at the bargaining table and invest in our pilots," said Chris Norman, chair of the FedEx ALPA master executive council.

FedEx did not immediately respond to a Reuters request for comment.

Its shares erased gains to trade roughly flat after the announcement.

Pilots are pushing for better contracts at airlines and parcel firms amid a shortage of aviators. Earlier this month, Southwest Airlines Co's pilots union said its members had approved a strike mandate by an overwhelming majority ahead of the busy summer travel season.

Under U.S. law, pilots cannot walk off the job until the National Mediation Board grants them permission.

The board must first decide that additional mediation efforts would not be productive and offer the parties an opportunity to arbitrate. If either side declines, both parties enter a 30-day "cooling off" period, after which pilots and management can engage in self-help - a strike by the union or a lockout by management.

(Reporting by Nathan Gomes in Bengaluru; Editing by Devika Syamnath)