Finally, the Spain's government opened the air space:
http://www.reuters.com/article/2013/07/03/us-usa-security-snowden-idUSBRE9610C520130703The plane landed at Gran Canaria airport, to be precise.
Personally, I think this is a bit shameful. On one hand, US government and CIA treat European allies like enemies (I think Merkel or someone stated something similar), on the other hand European governments act like fearful vassals. It's just a personal opinion, but I think it might be a good thing (and even convenient) for Europe showing some independence, since we are living in a multi-polar world and not in the Cold War.