In total, about 200 planes were built by the company.

That is because the first planes built are the most expensive.

The House proposal would end the program after the 15 planes are built.

By the time it was retired in the 1960s, some 3,900 planes had been built.

"The bottom line is that if we can't solve the environmental questions, the plane will not be built."

But even before a single plane was built, the program's costs soared at least $1.6 billion over budget.

Some planes built in the same era have more than 100 parameters.

Electronics, not building planes or ships, is expected to be the big military business of the future.

Some skeptics say the proposed plane will never be built.

The plane used in the test today was built in 1971.