Take the late red-eye that's unreliable? (3-2-5)
I believe the answer is:
fly-by-night
'unreliable?' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for fly-by-night that I've seen before include "Untrustworthy person, likely to abscond" , "Cowboy" , "Unreliable, shady" , "Unreliable (in business)" , "Unreliable - person who departs secretly to avoid debts" .)