The most common and most likely answer to this crossword clue is the 10 letter word TRAJECTORY
I've seen this crossword clue in The Daily Telegraph
T
R
A
J
E
C
T
O
R
Y
Buddy explains!

The straight part
We know that "flight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flight = trajectory.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.
What does TRAJECTORY mean?
TRAJECTORY noun- The path an object takes as it moves.
- The path of a body as it travels through space.
- The ordered set of intermediate states assumed by a dynamical system as a result of time evolution.
- A course of development, such as that of a war or career.