This happens at least once a week worldwide and usually on domestic flights when pilots are in a hurry to shuttle passengers, according to Gunnar Kuepper, chief of operation with Emergency and Disaster Management Inc. in Los Angeles.
Transportation officials investigate every incident and fine or suspend any pilot who is not following proper procedures.
"I cannot imagine an Air France pilot would overshoot a runway in spite of a severe weather warning."
What is a red alert?
A red alert is called when lightning hits too close to the airport. It's an automatic system that, when activated, clears ground crew from the apron -- or the part of the landing area where planes saddle up to the terminal. During a red alert, planes can leave and come into the airport. But it's unsafe for ground crew to guide them anywhere, so passengers and pilots have to just sit tight.
The visibility of the airport was, at its lowest, six kilometres yesterday. However, Greater Toronto Airport Authority spokesman Steve Shaw said that distance is well within the airport's comfort zone.
"The major problem with the weather was with the thunder cells going through setting off the red alerts," Mr. Shaw said. "It caused a backlog of traffic."
No plane has overshot the runway at Pearson in recent memory, he said.
Runway 24L is the newest of the five runways. It was built in 2002, he said.
What was the weather at Pearson?
"At 4:04 p.m. there were winds gusts from the northwest at 33 knots, a bit more than 56 kilometres an hour. The gusts were associated with strong thunderstorms. It was fairly warm and humid, with heavy rain in the area," said Robert Lefebzre, director of services to Aviation and Defence in Environment Canada.
How often do planes gets hit by lightning?
Non-fatal incidents such as lightning strikes are not recorded, making it difficult to determine how often they occur.
In the 1960s one plane crashed after it was struck by lightning in mid-air, he said. In the 1980's two planes crashed in South America after they were hit by lightning. In each instance everyone on board was killed.
Why might the back of the plane have been on fire?
Usually there are fuel tanks in the back of the plane. In a crash situation it is not unusual that a fire would start in the back where the auxiliary power unit is housed. It provides internal power for the plane.
Why didn't the wings of the plane catch on fire?
If the plane's fuel cells were full, the fire would have been more extensive, perhaps with an explosion.
It's unclear whether the fuel cells in the wings of the plane in yesterday's accident were full.
An A340 could fly from Paris to Toronto and back on one fill-up, Mr. Kuepper said. An airline may choose where to fill up based on fuel prices.
"Everyone is lucky there was not a lot of fuel on board," he said.
What factors may have caused the incident?
Bad weather, computer malfunction, pilot error may have played a role. The Airbus in yesterday's accident had been flying for six years, making a maintenance problem with the plane unlikely. While it is impossible to immediately know what the cause was, it was likely a combination of factors.
Will the burning fuel pose an environmental hazard?
"There will be very little environmental impact. Our team is out there checking Etobicoke Creek, looking for jet fuel. We haven't found anything to be concerned about, particularly since the fire has already been put out," said Brian Park, environmental officer at Spills Action Centre, Ontario Ministry of Environment.