North American pilots are pressing for higher salaries and better scheduling after aviators made big gains in a recent deal with Delta Air Lines that delivers a 34% pay increase over four years.

"Pilots at Air Canada are working at a steep discount compared to our North American competitors," the letter from the Air Canada Pilots Association (ACPA) seen by Reuters said.

"Our membership will not accept concessions and expects the next agreement to be historic in terms of gains."

ACPA said that its leaders must decide by May 29 whether to stay within the framework of a 10-year-agreement reached in 2014, or use a type of escape clause to enter into full negotiations this year.

The union said it would consider remaining in the framework if the Montreal carrier offered a "substantial proposal" that recognized the worth of Air Canada pilots.

Air Canada, which reports quarterly earnings on Friday, was not immediately available for comment.

The airline's estimated 4,500 pilots have received a 2% wage increase per year since 2014. The country's inflation rate was running at 4.3% in March, a 19-month low.

ACPA, which plans to join the larger Air Line Pilots Association (ALPA), has said Delta's latest hourly pay rates are up to 45% higher than the current rates at Air Canada.

Labor unrest has risen at North American carriers as pilots seek to make gains after traffic rebounded from COVID-19 lockdowns. Some airline executives fear hefty pilot raises will inflate fixed costs and make it tougher to repair debt-laden balance sheets.

United Airlines pilots are picketing on Friday. Pilots at WestJet Group, Canada's second-largest carrier, could strike as early as May 16, if notice is given on Saturday.

WestJet said on Thursday that the carrier was "making progress at the bargaining table."

(Reporting by Allison Lampert; Editing by Jamie Freed)

By Allison Lampert