CHICAGO (Reuters) - United Airlines has rehired 600 flight attendants and expects to bring back about 850 more later this year as increased passenger demand means more planes are flying near capacity, a company spokeswoman said Sunday.

The bankrupt airline, a unit of UAL Corp, said the 600 will return to work by August 9, and the second group will be brought back by the end of November.

The flight attendants were laid off following a downturn in airline travel in the wake of the Sept. 11, 2001 attacks.

"By the end of the year, we expect to have all of our flight attendants on furlough back," said United spokeswoman Robin Urbanski.

United, the No. 2 U.S. carrier, is embroiled in a dispute with its flight attendants, who have threatened to strike over the termination of company pension plans.

United won court approval in May to shift its four pensions to U.S. government insurers, a move that would save the carrier $645 million a year, while eroding employee benefits.

The Association of Flight Attendants, representing United's flight attendants, is the only union that has not yet negotiated a replacement retirement plan for its members.

United, based in the Chicago suburb of Elk Grove Village, Illinois, is aiming to emerge from Chapter 11 bankruptcy protection in the fall. The airline has been in bankruptcy since December 2002.