Air Canada’s check-in counters were back online Monday after a massive network outage snarled travellers who were trying to board their flights.

It is not yet known what time the outage occurred, but travellers were tweeting about the delays caused by the outage just before noon.

Read coverage below from CityNews reporter Amanda Ferguson and cameraman Tony Fera, as well as tweets from travellers:

“We’re currently experiencing an interruption at our customer contact centres and http://www.aircanada.com. We apologize for any inconvenience and are working towards restoring our service as quickly as possible. Thank you for your patience,” Air Canada said in a tweet.

Air Canada customers in Canada and around the world were unable to check in or book a flight after a malfunction in the company’s system.

There were long lines reported at airports, including at Pearson International Airport, as well as in Vancouver, Montreal, and Calgary.

“Air Canada is experiencing a network outage nationwide, and departing passengers are being checked in manually, which is causing a bit of congestion in the terminal,” Calgary International Airport said in a tweet.

Departing passengers were being checked in manually, with some people tweeting pictures of their handwritten boarding passes.

My first hand written boarding pass ever (at least that I remember). Air Canada's systems are down for the last 90 minutes so expect cascading flight delays today #aircanada #travel #canada pic.twitter.com/aMBxiwpuie — Jim Harris (@JimHarris) March 12, 2018

At first, it appeared the outage was only in Canada, but check-in counters around the world were also impacted.

In Toronto and elsewhere in Canada, the system issues came as travellers were heading out of town for March break.

Vasudha Sharma, a digital broadcast journalist, tweeted that around 100 or more passengers were waiting to get checked in at Pearson.

One traveller told CityNews flights could not depart since crews could not access the weight of the plane. Some planes reportedly unloaded passengers.