I doubt that airlines give free flights. With a copy of your Compostela, you can get three free meals in the following three days (or is it 9 meals total?) at the Parador Hotel (Dos Reyes Catolicos) by being one of the first 10 pilgrims at each one. The competition is fierce, so you probably will have to get there an hour or more before the meal. It is first come, first serve, and the few times I tried it, it looked like the same people trying at every meal. You enter through the garage entrance and check in with the guard there. He is barely civil, having to deal with complainers (me) and freeloaders (everybody else) three times a day, so don't expect anything more from him than waiting to see if you are one of the first ten. Pilgrims try to hold places for friends that are not waiting, or stop early to leave a copy and reserve a place in line. Sometimes that seems to work, most of the time you have to be present to be counted in line. Pretty women seem to get preference, but that is the case in a lot of places in Spain. Korean pilgrims seem to have made it part of the routine, like hugging the St. James statue, so often the first ten slots are all-Korean. For 20 Euro, you can have a first class brunch in the hotel dining room at the morning hour of your choosing, which was my favorite activity in Santiago.