Can't see the problem with this really ?
It would seem to have a gramatical purpose when talking about one of many. For example if asked what flight you were travelling on, it would not be incorrect to say the 10:30 flight as opposed to just 10:30 flight.
If a flight is checking in and announces itself as the skylight 4546 it would seem to emphasise the flight as being one of many which may well be the case. Given that the actual number is the prime differentiator it can be argued that the use of the leading the is redundant.
Given the need to keep R/T calls to a minimum it seems a bit at variance to add a word, but beyond that I can't really see why anyone cares.