Seat62K (and others I might say)
A friend told me yesterday that El Pais reported that the aircraft used all the runway.
Please just look at the basic facts
The aircraft started it's takeoff run around the start of 36L. It accelerated, rotated, got airborne, landed back on the runway, veered to the right, then went off the runway, then went off the surface alongside the runway, then went down into the ravine, and once there broke up / decelerated / caused an "accident site". Some of that is conjencture / rumour / assumption, but in general seems a fair summary?
That accident site, by pretty near certainty, is approximately 80% of the way along 36L, and displaced to the right. To end up there, yet use all the runway, it must have turned round and come back from the N? Do you really believe that
I would suggest therefore the "rotate" point, whether or not intentional, was roughly halfway down 36L, and very unlikely >70%.
Re Density Altitude: Unliklely to be major factor IMHO. DA is more significant in landing, where it alters your energy management on approach, flare technique (TAS/RoD), and most significantly LDR. Whilst you could try and translate that into takeoff, in practice it is "looked after" in the Perf Calculations, one of the longest runways in Europe, a SH aircraft, twin engined, and takeoffs being critical in V speeds / IAS terms, which are not affected by DA.
NoD