I am not sure if this is pertinent to the Madrid crash today but I spent some quality time and long delays in the Madrid airport on the way through to Monaco in late 2006. At one point 3 of us were able to get out of the airport across the pedestrian walkway to the parking areas - on the other side of the main passenger pick-up/drop off, to sit outside on the grass.

The door was unlocked and we were able to get outside and back in through this in plain view of anyone monitoring the passenger drop-off in front of the airport. We were inside secure areas waiting for our flights. Given the tone of security at the time, it may be possible that this door is still unlocked today.

If the crash today in Madrid has anything to do with a breach of security and the explosion upon take-off due to a bomb, I would suggest this point of entry be reviewed.