UPDATE 1-Pratt & Whitney gets $491 mln F-35 engine contract

(Adds details of contract, background, stock action)

CHICAGO, Sept 25 (Reuters) - United Technologies Corp's (UTX.N) Pratt & Whitney unit said on Thursday that it has been awarded a contract worth up to $491 million to provide propulsion systems for F-35 Lightning II fighter aircraft.

Lockheed Martin Corp (LMT.N) is working on the $299 billion F-35 Joint Strike Fighter program for the Pentagon, the most expensive U.S. arms buy in history.

Engine maker Pratt & Whitney said the contract is for 12 F-35 production aircraft, including six capable of short takeoffs and vertical landings.

The company said the first propulsion systems will be delivered starting in the third quarter of 2009.

In trade on the New York Stock Exchange, United Technologies shares were up 42 cents at $60.05.