Would it be natural to use "kadar" in the answer and if so how?
Uçuşa kadar beş saat var.
Why şa at the end of Uçu ? Does this end mean anything ?
Uç is the root of uçmak (to fly). Uçuş is the noun form (flight). Uçuşa is the dative case of it.
I would have translated this sentence as "The flight takes five hours". I guess that's wrong, so how would you express the duration of a flight?
You need sürmek. Uçuş 5 saat sürüyor.
Could you write Önce uçustan beş saat var