United Airlines has gone on to become one of the largest airlines in the world and the number United Airline Reservations made every day is a testament to that fact. It is considered to be the chief airline in terms of its fleet size, profits collected, number of passengers carried on its planned flights and scheduled passenger-miles flown. This leading airline also provides the option of online check-in. This capability is very helpful when you’re running late at the airport as it allows you to procure your boarding pass on your mobile phone. United Airline Reservations passengers from these travel classes enjoy priority check-in, security check and boarding. They are also qualified to receive their checked baggage first at the destination airport after they land and exit the aircraft.