Terminal 4 is the Iberia terminal. There are probably a lot of Spaniards who'd like to bomb it! (One of the worst, most customer-unfriendly airlines in the world.)
But seriously, the timing of this is a little odd. Zapatero has practically announced that he is "negotiating" with ETA to give away Pais Vasco, and it's hard to see how they'd benefit from this.
I don't know livius, but I can look at the middle east and see how short-lived the "peace agreements" are ("Palestine" vs Israel). Maybe it's a similar situation here in Spain.
The last Iberia flight I was on I was seated in first class - sullen flight attendents, really, really bad service, lousy food.
My wife had to fly in tourist class ;) and it was the worst experience flying she's ever had to endure. My experience was on Aerolineas Argentinas is a close second. I literally kissed the tarmac when I got off the plane - it was scarey.
Probably a work accident...