Noun
English Wikipedia has an article on:flight numberWikipedia
flight number (plural flight numbers)
(aviation, travel) A callsign assigned to a commercial flight for the purposes of reservation and ticketing, typically consisting of a 2 character airline code and a 1 to 4 digit number to indicate a particular service.
Flight number 9I 509 will depart from Bengaluru at 11.40 AM and will reach Kalaburagi at 1.20 PM. Source: Internet