WestJet CEO Diederik Pen in an open letter to customers says the company experienced a system-wide outage on Saturday due to a cooling issue in its primary data centre. It resulted in a severe disruption to service with more than 200 flight cancellations across WestJet’s network and significant delays throughout Saturday and Sunday.

Pen says the technology outage has been resolved and all systems are online, but the airline is still experiencing some instability and because of the scope of the outage customers can expect further disruptions, delays and cancellations.

Anyone with travel plans is asked to check the WestJet app or WestJet.com for the most up-to-date information on their flight. In order to help guests with imminent travel plans, the company is asking all other guests to refrain from contacting them until 72 hours in advance of their flight so they can prioritize calls. If you go to the airport to deal with your change in flight, Diederik Pen says they can’t help you, but rescheduling will be communicated via email.