In general , the lower the number. The more prestigious the flight route is for that particular airline. one or two-digit numbers are typically assigned to popular route -- usually for the long distance variety -- such as United flight 44 from Newark to london .if you find yourself on a flight with a low number ,it's pretty safe bet that your flight is a regular moneymaker for the airline.
Flight numbers comprised of four-digit sequences starting with 3 or higher are ordinarily an indication of a case - share flight.Think U.S airways Express where you are flown between destination on behalf of U.S air . You might purchase your ticket through U.s. Air,but the plane and crew belong to a separate partner airline.