Crates preparing to take off with other holidaymakers? (7,5)

I believe the answer is:

packing cases

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'crates' is the definition.
(packing case is a kind of crate)

'preparing to take off with other holidaymakers?' is the wordplay.
I cannot really see how this works, but
'take' could be 'pack' (synonyms) and 'pack' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Times.

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