"When are you flying?"
Of course it's not a noun, but "Kiedy lecisz/wylatujesz?" means the same things as "Kiedy jest twój lot?", so we decided to accept it.
Sure, I will happily tell you why it's wrong :) It's because "When are you flying?" asks for the time of departure, and "Kiedy przylatujecie?" asks for the time of arrival.
It's used for flying using wings. It surely works for birds and other flying animals, but I'm not sure if it should be used for a plane. Even if it's not wrong, it sounds at least unusual.
If it were to work here, you'd need "frunąć" here, though: "Kiedy fruniesz?".
You will probably be safer just using "latać" and "lecieć" while understanding what "fruwać"/"frunąć" mean.