Flees by air? (5,6)

I believe the answer is:

takes flight

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'flees by air?' is the definition.
'takes flight' can be an answer for 'flees' ('take flight' can be a synonym of 'flee'). I am not certain of the 'by air?' bit.

'flees by air?' is the wordplay.
'flees by' becomes 'takes' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'air?' becomes 'flight' (flight is a kind of air).
'takes'+'flight'='TAKES FLIGHT'

Can you help me to learn more?

I've seen this clue in The Irish News.

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