The most common and most likely answer to this crossword clue is the 3 plus 2 plus 3 plus 3 letter word PIE IN THE SKY
I've seen this crossword clue in Financial Times
P
I
E
I
N
T
H
E
S
K
Y
More clues leading to the result PIE IN THE SKY
- Improbable promise of high tea?
- Fantastic food that’s flying?
- Dish served up? That’s unrealistic
- Food on plane journey is something you’d dream of being good
- Possible future good a source of inflation for air travellers?
- Unrealistic expectation of high tea?
- Hot food on plane? That's unrealistic
- Something delusional like high turnover?
Buddy explains!

The straight part
We know that "Fantastic/food that’s flying?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fantastic/food that’s flying? = pie in the sky.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.