CALGARY —WestJet pilots are again seeking to form a union, the Air Line Pilots Association, International said Thursday.

It says pilots at the Calgary-based airline (TSX:WJA) filed membership cards with the Canada Industrial Relations Board to hold a vote to be represented by the world’s largest airline pilot union.

The association says it expects a secret-ballot election will be held in May after the board verifies the membership cards.

WestJet pilots voted to reject a unionization drive by the WestJet Professional Pilots Association in 2015.

ALPA president Capt. Tim Canoll said in a news release that a vote to join the union will give the pilots the resources to begin negotiations for a collective bargaining agreement.

WestJet didn’t immediately respond to a request for comment.

The Air Line Pilots Association represents 55,000 pilots at 32 airlines in Canada and the U.S., including Air Transat, Air Georgian, Bearskin, Calm Air and Jazz Aviation.

The Canadian Press