Porter Airlines says it's back online and back in the air.

Its most recent tweet says all of its systems are back online and the company is asking passengers to check their flight status at flyporter.com.

About two dozen flights have been cancelled to handle the backlog, says the airline.

On Sunday morning, the Toronto-based airline grounded its flights due to a computer outage. Its website was also affected.

"We apologize for the delay and appreciate your patience," said one of the tweets.