The most common and most likely answer to this crossword clue is the 9 letter word PREFLIGHT
I've seen this crossword clue in The Guardian
P
R
E
F
L
I
G
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T
Buddy explains!
The straight part
We know that "Before taking off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case before taking off = preflight.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 PREFLIGHT mean?
PREFLIGHT noun- An inspection of an aircraft before the start of a flight.
- To perform an inspection of an aircraft before the start of a flight.
- Taking place before the start of a flight.
- Serving to confirm that requests can be accepted, before sending an actual request.