WestJet Pilots are going on strike.

The Airline Pilots Association International (ALPA), the union representing Westjet Pilots issued a 72 hour strike notice to the airline on Monday evening. The notice allows the union to begin job action as early as Thursday evening.

The ALPA posted an update on their website saying at 3:00 a.m. ET on May 19, the WestJet pilots plan to begin lawful job action, which could include grounding all aircraft and effectively shutting down operations.

“After nine months of negotiating, management still fails to understand today’s labour market conditions,” says Capt. Bernard Lewall, chair of the WestJet ALPA Master Executive Council (MEC).

“Without the economic and job security improvements our pilots require, WestJet will be parking planes, as they will not have enough pilots to operate them or accomplish its own growth strategy.”

Harvard Media News has reached out to WestJet for comment and will provide updates as they become available.