At 13:20, the plane taxied out towards runway 36L for take-off. Five minutes later, Captain Antonio Garcia Luna received clearance for take-off. A red light in the cockpit alerted him to the fact that the external temperature gauge wasn't working correctly. The Captain decided to turn back to have it fixed.

According to Spanair, the problem was overheating in the de-icing system, rather than any dysfunction affecting the temperature gauge itself. With the Captain's approval, the mechanic de-activated the de-icing system, since weather reports excluded any risk of icing-up during this flight to the Canary Islands.

This incident, which occurred just before the flight, is a subject of debate in Spain. Especially since the Transport Minister, Magdalena Alvarez, revealed on Friday that "the airline considered replacing the plane with another one, registered F-HFS, but in the end told the airport authorities that it had decided to go ahead" with the original aircraft.

The airline almost changed planes just before the flight

Even though Spanair refutes this version of events, the taped conversation between Spanair's operations manager and airport control at Barajas confirms that the airline did consider changing planes. Excerpts from that conversation were published in the Sunday edition of the daily newspaper El Pais.

At 13:49 – less than an hour before the accident – a Spanair employee rang the operations manager at Barajas airport and explained, "We're bringing 5022 (Flight JK5022) back to the parking area and changing that 'plane for Hotel Fox Sierra (HFS, the registration number of the new aircraft). "

The airport officer on duty at the operations centre logged the request. Then the Spanair employee added, "Can you give me Gate Charlie 49? The 'plane's going to go out from there. We've already got people down there. "

The conversation lasts three minutes and 38 seconds. Amid the background noise, the Spanair employee can be heard talking to a colleague at the same time. Finally, just before hanging up, the Spanair employee says that the decision to change 'planes may not be definite:

"Oh, they're going to wait a bit. I don't know if I'll have to call you back, because maybe they're going to solve the technical fault. "

Lack of power

It was 14:25 when the pilot made his second attempt at take-off in the same aircraft. Different witnesses, including airline pilots, say that the 'plane had a much longer take-off run than others of its type – about 500 metres extra. The MD-82 got about 50 metres into the air then veered off to the right.

Some experts say that the long take-off run supports the theory that the aircraft didn't have enough power. The Spanish press has suggested that it was overloaded: it had a full complement of passengers (172 people), a lot of luggage, and was taking off from a runway at an altitude of 600 metres in a very hot period (40 degrees Celsius on the runway).

Others say that the faulty temperature gauge can't be left out of the equation, because information supplied by that gauge is used in calculating the necessary engine power.

There's one more mystery. The reverse thrust on the 'plane's right-hand engine had been deployed. This system is normally used to slow a 'plane on landing. Several theories are under consideration: that the reverse thrust self-activated – which would explain the lack of power observed by witnesses, and the 'plane's veering-off to the right. Or it may be that the system was activated by the crew in a desperate attempt to slow the 'plane.

The black boxes are currently being analysed in the United Kingdom. The official inquiry commission is due to release an initial report in a month's time.