What air traveller needs, having meals provided? I don’t know (8,4)
I believe the answer is:
boarding pass
'what air traveller needs' is the definition.
(boarding pass for a flight)
'having meals provided? i don't know' is the wordplay.
'having meals provided?' becomes 'boarding' (as in a boarding house).
'i don't know' becomes 'pass' (e.g. response in a quiz).
'boarding'+'pass'='BOARDING PASS'
(Other definitions for boarding pass that I've seen before include "travel document" , "prerequisite for high-flyers?" .)