Multi Engine Aircraft

The biggest piece of aerospace business, possible the last big piece ever, is the F35 fighter program. They are talking about a thousand of them. The biggest piece of business in the F35 is the engine. Typically the engine accounts for a quarter to a third of the price of the airframe (plane less fancy electronics) Currently Pratt and Whitney's F135 engine is built, tested, bought, and installed in the F35.
However, Congress likes the idea of a second engine supplier for the F35, and so, there is $485 million of development money for GE to develop a second engine design. GE, and the congressional delegations from every state with a GE plant think this is a wonderful idea, the competition between Pratt and GE is supposed to keep the price of the engine down. After those development costs are paid down of course.
The Pentagon, (and Pratt) think $485 million could be saved this year, and a like amount in future years, by canceling the second engine and going with the existing design. As an old squadron level maintainance officer myself. I'm all in favor too. The thought of having a squadron of fighters with two different engines is unpleasant. You need two sets of special tools to work on them, two sets of spare parts, you have to train your guys on both engines, and you open up a whole world of nasty possibilities for maintainance errors. Not good.
In the old days, engines had multiple aircraft. The J47 powered the F86, the B45, B47, and others. The J57 powered the B52, the F100, the F101, the F102 and the early 707's. The J75 powered the F105, F106, U2, and later 707s. The thought of having two engines to power a single fighter is a kind of technological richness, or perhaps over indulgence, that we didn't have back when I was a flight line maintainance officer. Sounds like time for a cost cut here. Usually when the Pentagon doesn't want something and Congress does, there is pork involved.