LOS ANGELES, April 15 (Reuters) - United Airlines, a unit of UAL Corp UAUA.O, will require obese passengers bumped from full flights to purchase two seats on a subsequent flight, matching the policy of some other carriers.

The change brings the Chicago-based in line with eight other airlines including Continental, Delta, JetBlue and Southwest, United spokeswoman Robin Urbanski said on Wednesday.

“Last year we had 700 complaints from passengers who had to share their seats,” she said.

Under the new policy, obese passengers -- defined as unable to lower the arm rest and buckle a seat belt with one extension belt -- will still be reaccommodated, at no extra charge, to two empty seats if there is space available.

If, however, the airplane is full, they will be bumped from the flight and may have to purchase a second ticket, at the same price as the original fare, Urbanski said.

If the bumped passenger chooses to cancel the trip, the ticket will be refunded with no additional charge.

The policy is effective immediately. (Reporting by Deena Beasley; Editing by Richard Chang)