The 20 August crash of a Spanair Boeing MD-82 occurred in hot and high conditions that would have reduced aircraft performance margins.
Persistent reports from multiple sources suggest its left engine failed and caught fire, but this nor any other information had by 22 August been confirmed by the Spanish authorities.
Madrid's main airport has an elevation of 2,000ft (610m), and the weather was fairly hot at 28°C (82°F) or 29°C (see box).
Heat and altitude both markedly reduce the power a jet engine can produce, although this is taken into account in take-off performance calculations.
Barajas's Runway 36L is very long to accommodate take-offs in summer conditions, which at the time included a very light wind that was varying between southerly and south-westerly.
The MD-82 was carrying a full load of 172 people, including 10 crew, four of whom were off duty.
The aircraft was fuelled to fly to Las Palmas in the Canary Islands, a distance of 1,765km (970nm), which is comfortably within the aircraft's range under the conditions.
At some point well into the take-off the pilots lost control, and the aircraft veered away from the runway to the right, and the widely dispersed wreckage eventually came to rest in a shallow gully between runways 36L and 36R.
The aircraft is believed to have got airborne, if only briefly, above the runway, but then to have landed back on it before veering off.
The flight data recorder and cockpit voice recorder have been recovered.
A fierce fire appears to have been the cause of most casualties because the medical services are having problems identifying most of the bodies. The number of deaths has been put at 153, with many of the 19 survivors suffering serious injuries.
The flight was late taking off because, about 2h earlier, the crew had returned the aircraft to the ramp with a fault that is believed to have been an overheating pitot tube, although the authorities have not confirmed this.
See blogs, images and news on the Spanair MD-82 crash in Madrid on our Safety Channel