The Real Decreto says that a pilot to exercise privilege in a commercial airplane has to know English and the language of the State and in this case Spain.
I don't know if I am the only one that as realized that in Greece Aegean Air asks greek..all the company in Swiss,Germany,Austria have been asking German since forever.
As personal opinion, this is completely wrong as suppose a big barrier, but nothing we can do.
Aloa
Ps last Iberia pilot assestment they were asking for Spanish level 6.