At this point, I'm used to seeing UNICEF envelopes on my meal trays. I've heard a lot about Alaska Airlines' prayer cards (see Salon's Ask the Pilot on the subject, sub/ad supported day pass req.). Next up is tray advertising. Hmm- if they serve less food, you can see more of the ad space from the start. From WOAI:
When air travelers flip down the tray tables on their America West Airlines flights, they'll be getting more than the usual peanuts or pretzels later this month. They'll also be getting advertising.
Advertisers on board include Visa, Mercedes-Benz USA, The History Channel and Bank of America.