Overweight passengers hoping to travel on United Airlines may have to buy two tickets to fly the friendly skies.

The third largest U.S. airline announced Wednesday that it will join other carriers and start charging passengers for two seats if they can't properly fit into one.

United made the change as a result of the hundreds of complaints it receives each year from customers who "had to share their seat with the oversized guest," United Spokeswoman Robin Urbansky told Blo****erg.com.

According to the airline, the policy will be enforced only in the event that the passenger can't be relocated next to an empty seat. If the flight is full, the passenger will have to change their ticket to the next available flight and purchase a second seat for that flight.

United is the fifth major airline to adopt a policy of this kind.

The new rule applies to tickets purchased on or after March 4, 2009, for travel on or after April 15, 2009.