UPDATE 1-Pentagon again omits funding for 2nd F-35 engine

* Fourth year of Pentagon effort to kill program

* Congress keeps adding funding back in (Adds details, byline)

By Andrea Shalal-Esa

WASHINGTON, May 7 (Reuters) - Defying Congress for a fourth straight year, the Pentagon on Thursday submitted a budget proposal for fiscal 2010 that once again zeroed out funding for an alternate engine for the F-35 being developed by General Electric Co (GE.N: Quote, Profile, Research) and Rolls-Royce Group Plc (RR.L: Quote, Profile, Research).

In each of the past three years, the Defense Department has pressed Congress to scrap the second engine for the F-35 fighter to save funds, but lawmakers have repeatedly added in funding to keep the alternate engine program alive.

The F-35, or Joint Strike Fighter, is the newest family of advanced fighter planes being built by Lockheed Martin Corp (LMT.N: Quote, Profile, Research) for U.S. forces and eight partner countries.

The market for the F-35 engines is estimated to be worth $100 billion over the life of the program -- a huge boon for engine maker Pratt & Whitney, a unit of United Technologies Corp (UTX.N: Quote, Profile, Research), which developed the engine already in use in early production models of the aircraft.

Congress initiated the second engine program in 1996, and has provided approximately $2.5 billion in funding for the program since 1997, according to a February 2009 study by the Congressional Research Service.

The nonpartisan research arm of Congress said the alternate engine program was expected to need an additional $900 million through 2013 just to complete development of the F136 engine. Including expected procurement, the program is valued at $7.2 billion, according to government watchdog groups.