1/2 price airline tickets

[Martin Ray]

Hi -- I understand that, with a Compostela in hand, Spanish airlines
(Iberia) will give a 50% discount off their regular fares.  (perhaps it
also helps with bus travel afterwards, too?). Anyway, if this is in fact
true, then is there a way, IN ADVANCE, to take advantage of this
opportunity while booking round-trip tickets from the states? I'd
probably wish to fly to Madrid, or possibly even Pamplona (via Madrid).
Your ideas or help would be appreciated......Martin