The blaze that erupted after the crash delayed the rescuers
A passenger jet taking off in trouble and veering into a rocky ravine brought tragedy to Madrid airport.
Experts say because the crash happened on take-off rather than landing, the plane would have been heavily laden with fuel.
Then, when the plane veered into a dry river bed it broke up and burst into flames, setting light to surrounding vegetation.
The fire delayed rescuers from reaching any survivors inside the fuselage.
Take-off and landing can be the most dangerous points of any flight, Chris Yates, aviation analyst for Jane's Information Group, told the BBC News website.
"As the aircraft is rattling down the runway, there is a point of no return which is the speed close to lift-off," he said.
"At that point, the aircraft is going at such a speed that it has to reach for the sky. The plane has to be airborne even with an emergency on board."
Eyewitnesses have said that one of the jet's engines was on fire when it took off.
Pilots are trained to deal with many emergencies, including engine failure on take-off.
There are also on-board systems to deal with engine fires, said Mr Yates.
Investigators will be looking for information on what caused the engine fire, and what maintenance, if any, was made to the plane to allow it to leave Madrid, he said.
"They will also be looking at the sequence of events after that fire broke out, including what the pilot did and if the on-board systems functioned properly."
Pilots have expressed concern about the topography alongside runways
A practising airline pilot of 20 years' experience, who declined to be named, told the BBC that pilots were concerned about runways being built over dry riverbeds.
He said that uneven terrain alongside runways increased the dangers if an aircraft failed to take off.
"It is a constant concern to pilots that the surroundings of runways, with more thought and better civil engineering, could reduce aircraft break-up in a crash. Basically, people die in planes that burn or break up," he said.
However, he added that pilots had been impressed by the speed and the scale of the emergency procedure in Madrid.
"It was obvious that this was a well-prepared and rehearsed emergency plan," he said.
Other tragedies involving passenger jets during take-off include the Concorde crash in Paris in 2000 in which more than 100 people were killed.
In 1985, the engine of a Boeing 737 caught fire at Manchester airport, killing 55 people.