Translation:What is the temperature in the airplane?
We have the same construction in English:
"What is it for lunch? Soup again?"
"What is it for them in the deal?"
"What is it for me if I eat well?"
Though more commonly used is a related structure with the pronoun "there" in lieu of "it":
"What is there for eating in the kitchen?"
"What is there for weather today?"
"What is there for snow on the slopes?"
"What is there for things to do?"
In this case "there" serves as an existential pronoun exactly like det does in det finns.
To paraphrase a famous quote, perhaps we are "two nations divided by a common language"? :-) I too have lived in very different parts of the US and I have not heard phrases quite like those. Still, thinking about the Swedish version that way helps me remind so it's all good.