Harrowing situations quietly play out in the skies above Toronto every day, and it takes the expert know-how of both pilots and air traffic controllers to keep passengers and flight crews safe.

In one recent case of averted disaster, a flight departing the city last week was forced to issue a distress call shortly after departing Pearson Airport in a situation that very well could have ended in the loss of hundreds of lives if not for the quick thinking of the pilots and air traffic controllers involved.

YouTube channel You can see ATC offers a glimpse into the zero-margin-for-error situations that air traffic controllers encounter all too often.

In a video published this week, the channel documents the terrifying chain of events when a May 18 Air Canada flight departing Toronto Pearson International Airport issued an urgent Mayday call to the control tower amid a mysterious electrical odour detected aboard the aircraft.

Flight AC490 departed Pearson just before 6 p.m. last Thursday with 297 passengers aboard the Airbus A330-300 aircraft bound for Montreal-Trudeau International Airport.

It would not reach that destination on schedule.

During the flight's climb to cruising altitude, the control tower repeatedly instructed pilots to "maintain a speed of 270 knots" to no response. After a brief silence, the air traffic controller attempts to get the pilot's attention, saying, "Air Canada 490, departure."

The crew then finally responds to the tower, asking them to "stand by, we have an issue." Soon after, the pilot levels off at 11,000 feet on a course headed east over Lake Ontario and is asked by the tower if they would like to proceed on course for Montreal or return to Toronto.

Moments later, the pilot responded with the most urgent distress call in aviation terminology, saying, "Air Canada 490, declaring a MAYDAY-MAYDAY, electrical smell in the cabin, returning to Toronto."

After declaring its passenger count and fuel load, the pilot requested landing on Pearson's runway 23, and was granted clearance from the tower to land.

Arrival crews informed the pilots that rescue and firefighting equipment would be present for their landing, though, luckily, emergency crews would not be needed when the aircraft safely touched down.

A passenger on the flight tweeted that the flight crew remained calm and professional, though the passenger would miss a connecting flight as a result of the delay.

AC490 returned to YYZ after reports of electrical fire smell. All is good. @AirCanada crew stayed calm and professional. And now I missed my connecting flight AC818. Addio Venezia… pic.twitter.com/vpzBAePuXv

— GEL (@wheres_gar) May 19, 2023

Following the aborted takeoff, passengers got back in the air on a rescheduled flight that took off at 12:21 a.m. the following morning. Flight AC490 would eventually make it to Montreal at 1:35 a.m. on Friday, almost seven hours after its scheduled arrival.