Well having only dipped my toe into Spanish aviation (did my CPL there about 4 years ago) I did however get to know two things:
1. Iberia was then very much a closed shop, you literally had to be related to someone in Iberia to get an interview. Maybe that's common knowledge, maybe not, maybe it's not true anymore, but it was then.
2. If you are flying a Spanish a/c you will be automatically expected to converse with ATC in Spanish. I know it's not ICAO but there you go! Some would argue thats bloody dangerous but as I get older and greyer I can only remember the nice things about Spain of which there are many.