WestJet Pilots are going on strike if there isn’t a deal in the next 72 hours.

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.

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.”

Not long after the pilots issued strike notice, the airline sent out a news release of its own. WestJet was issuing “lockout” notice.

The decision to issue a lockout notice, in response to the actions taken by the union today, was not one that was made lightly, and we sincerely regret the inconvenience and uncertainty this continues to cause for our guests,” said Alexis von Hoensbroech, WestJet Group, Chief Executive Officer. “It is our responsibility to ensure the safety and complete control of our network at all times, to minimize the risk of stranding our guests, our crews and our aircraft. Our commitment and priority remains at the bargaining table, where we will continue to work around the clock to come to a reasonable agreement as soon as possible, in an effort to prevent labour action.”

Both sides have indicated they are willing to keep talking until the deadline, Thursday night.

–This story was updated with new information, including comment from WestJet–