The first time they tried to blow up the Madrid-Seville line. Then last Saturday, they tried to blow up the Madrid-Lerida line.
Furthermore, the terrorists who killed themselves when surrounded by police in Leganes last Saturday had a big mall as the next target. The terrorists had detailed maps of Parquesur Mall, half a mile away from the terrorists' apartment.
Btw, Parquesur Mall is a large complex; in addition to 200 stores, includes a multiplex movie theater (2000 capacity), a night club and a hotel.
I suspect al-Qaida is also planning attacks in a large mall somewhere in the US. No need to train pilots, just a few suicide bombers with nasty substances.
I hope our mall security is up to the task.