(CNN) — The Air Canada regional jet was scheduled to take off Sunday from Montreal Pierre Elliott Trudeau International Airport around 8 p.m.

Steering the one-hour flight were pilot Antoine Forest and a first officer, both “young men,” the top Federal Aviation Administration official would say, “at the start of their careers.”

They were bound for New York’s second-biggest airport, LaGuardia, where the crew of air traffic controllers was slightly smaller than its target of 37, with 33 employed and seven in training, the Transportation Secretary later would explain.

Such a setup wasn’t unfamiliar. Among factors the National Transportation Safety Board found led to last year’s midair collision of an Army Black Hawk helicopter and American Airlines regional jet that killed 67 near Washington, DC, was air traffic control’s “degraded performance,” with two positions combined in the tower.

That collision – the deadliest US commercial aviation accident in decades – had become the latest in a series of high-profile, fatal accidents renewing scrutiny of the airline industry.

On Sunday, US air travel also faced another significant strain: diminished Transportation Security Administration staffing owing to a lapse in funding for the Department of Homeland Security as federal leaders fought over immigration enforcement tactics.

As Air Canada flight 8646’s departure time approached, passenger Jack Cabot made his way to the gate. So did Rebecca Liquori, a mom heading back to her sons, 2 and 4, whose giggles she cherished.

It was after 10 p.m. when the CRJ-900 took off, en route to an arrival gate in East Elmhurst, Queens.

About an hour later – shortly after 11 p.m. – LaGuardia’s Air Traffic Control Tower got a radio message from the pilot of another flight, this one run by United Airlines.

His plane had pushed away from the terminal but would head back to it, he said, because of a problem with its de-icing system and a “weird” odor onboard the aircraft, an audio recording indicates.