Passengers and planes, non-stop
The first challenge for airline operational staff and the airport authority is to allocate gates for the incoming flights.
Assigning flights beyond the gates' handling capacity creates a backlog, even on a day with perfect weather conditions.
"There's so many people. It's non-stop, there's this fire hose that's constantly pumping out passengers and planes and if you try to stop it, there's this long residual effect afterward," a former pilot said.
On Monday night, however, those everyday challenges were compounded by the polar vortex storm system that slammed into the heart of North America, causing many other airports to reroute flights bound elsewhere to Toronto.
"They took on more than they could handle," said Bill Trbovich, a spokesman for the International Association of Machinists and Aerospace Workers, which represents Air Canada ground crews.
The ground stop was a Tier 2 stop, which affects only North American flights. But it wasn't possible to divert domestic flights to international gates because their passengers hadn't cleared border controls.
On the other hand, the pilot noted, planners don't want to be too cautious and under-book gates.
'It's a big deal because if you can't get to gate, you can't make money," the pilot said.
Marshallers couldn't get footing
Once planes hit the ground, they report to ground controllers, then to controllers for the apron, the area where aircraft are loaded and unloaded, refuelled or repaired. Planes first clear the runway, then the taxiway. If no gate is free, a plane may have to wait somewhere, even in the de-icing bay.
After planes approach the gates, they are guided by ground crews, the marshallers who give hand signals to the pilots and the wing watchers, who make sure the wings don't clip anything.
While the airport authority says runways were properly cleared Tuesday, the union representing ground crew said the approaches to gates remained covered in ice.
"You couldn't get your footing. If you were operating machinery like a baggage-towing cart or a baggage loader, you can't get any traction. If one of those vehicles were to slide and hit the aircraft, you could damage it and injure people," Mr. Trbovich said. "So as a result, everything had to slow down by 50 per cent."
He said it was the airport's responsibility to clean the aprons. Toby Lennox, vice-president of strategy development and stakeholder relations, acknowledged that ice had been a problem, noting that the chemicals used to clear it don't work well in extreme cold.
Trouble at the gate
Connecting the plane door to the passenger bridge can be tricky too, the pilot said.
"They're pretty skittish. If you have an icy surface or lots of snow underneath and if their tires spin, they'll shut down and then you have override."
The bridges' hydraulic systems were also icing up, Mr. Trbovich said.
"You know what it's like to be out in the cold, and especially that level of cold, everything slows down," Mr. Lennox said. "Your equipment freezes, hydraulic equipment works slowly. The crews, when they're out there themselves, are bitterly cold."
Everything slowed down
In the bone-numbing wind, ground crews struggled to manage a host of critical functions, including connecting the planes to land power to provide electricity without the need for aircraft engines or auxiliary power units. Mr. Lennox said that outdoor crews rotated, with periods inside to prevent them becoming too chilled. This is a routine practice at some other cold-weather airports. A senior executive at Minneapolis-St. Paul International Airport said it pairs up outdoor crews in extreme conditions and keeps them outside as little as possible.
Groomers came aboard to clean aircraft cabins and restock supplies. Baggage handlers unloaded cargo. The pilot said icy, cold conditions would have slowed those operations.
"Those ramps, they're windy, you're always touching metal, you're always dealing with frozen equipment … all these things start piling up. When you leave equipment running all the time, which would be the most logical solution, then they start running out of gas, which believe me, it happens a lot."
Mr. Trbovich said the ground crews worked eight– to four-hour shifts under wind gusts. There were no regulations curtailing their work hours, so some worked double shifts.
"Everything started slowing down," Mr. Lennox said. "Because of the volume that you deal with in a major international airport like Pearson, you do get more delays than you would at other airports."
Meanwhile, baggage choked the system
Because it took so long to process each plane, passengers had
exited long before their luggage could be removed from cargo holds.
Luggage was piling up, both on the tarmac and inside. At one point, there were more than 5,000 pieces of luggage waiting in a room, Mr. Trbovich said.
"There were planes on the apron that couldn't unload their luggage because there was no place to put it," he said.
Then all the problems multiplied
If the turnover at a gate is hampered, the problem compounds and worsens the backlog.
"When your plane doesn't leave, then the arriving plane has nowhere to go," the pilot said.
"All these things, they add up, they add up. And once the ball has been dropped, especially at a busy airport like Toronto, it's trouble for a long, long time afterward."