MONTREAL — Air Canada is warning travellers check their flights before heading to the airport as troubles caused by a key computer outage at the FAA impacts flights in the U.S.

Air Canada says the outage would have an effect on its transborder operations, but says it is not possible to determine the extent at this point.

Air Canada says it is putting in place a goodwill policy for affected customers to change their travel plans.

“Due to the recent FAA computer outage, we invite all customers travelling today to and from the USA to check their flight status here,” said Air Canada in its latest Twitter update.

CLOSE TO 5,000 FLIGHTS DELAYED

As reported earlier, the FAA issued a grounding order this morning for all departing aircraft out of the U.S., due to a problem with what is known as the Notice to Air Missions System.

The FAA lifted the order just before 9 a.m., but the delays and cancellations it caused are expected to ripple through the system.

The White House initially said that there was no evidence of a cyberattack behind the outage. President Joe Biden said he’s directed the Department of Transportation to investigate.

Whatever the cause, the outage showed the world how dependent its largest economy is on air travel, and how dependent air travel is on an antiquated computer system called the Notice to Air Missions System, or NOTAM.

Before commencing a flight, pilots are required to consult NOTAMs, which list potential adverse impacts on flights, from runway construction to the potential for icing. The system used to be telephone-based, with pilots calling dedicated flight service stations for the information, but has moved online.

Nearly 5,000 flights were delayed and almost 900 had been cancelled by around 10 a.m.

Long-time aviation insiders could not recall an outage of such magnitude caused by a technology breakdown. Some compared it to the nationwide shutdown of airspace after the terror attacks of September 2001.

“Periodically there have been local issues here or there, but this is pretty significant historically,” said Tim Campbell, a former senior vice president of air operations at American Airlines and now a consultant in Minneapolis.

Campbell said there has long been concern about the FAA’s technology, and not just the NOTAM system.

“So much of their systems are old mainframe systems that are generally reliable but they are out of date,” he said.

According to FAA advisories, the NOTAM system failed at 8:28 p.m. Eastern Time yesterday, Jan. 10, preventing new or amended notices from being distributed to pilots. The FAA resorted to a telephone hotline to keep departures flying overnight, but as daytime traffic picked up it overwhelmed the telephone backup system.

Breakdowns in the NOTAM system have been rare. The stop order by the FAA affected almost all flights of shippers and commercial airlines.

More than 21,000 flights were scheduled to take off in the U.S. today, mostly domestic trips, and about 1,840 international flights expected to fly to the U.S., according to aviation data firm Cirium.

With file from The Associated Press