What's the deal with airline food?

The joke “What’s the deal with airline food? The flavors are all so plane, and the prices are sky high” plays on the double meanings of the words “plane” and “sky high.” The word “plane” is a homophone for “plain,” which means lacking in flavor or interest. This part of the joke criticizes airline food for being bland. “Sky high” is a phrase that means extremely high or excessively high, which here refers to the high prices often associated with food purchased on an airplane. The humor emerges from the pun on “plane” and the metaphorical use of “sky high” to describe both the literal context of eating in the sky and the figurative sense of high costs, delivering a witty commentary on the quality and expense of airline food.