Long Beach, Calif. ? Boeing Co. said Friday it would start shutting down production of its cavernous C-17 military cargo plane at its Long Beach plant, marking the possible end of aircraft manufacturing in a region that once dominated the industry.

Unless Congress authorizes new orders, the decision could trigger a ripple of job cuts nationwide, including more than 7,000 Boeing employees and an additional 25,000 workers in 42 states that provide parts for planes still moving everything from tanks to troops around Iraq and Afghanistan.

Layoffs likely would not be immediate as Boeing has several dozen pending orders, enough to keep production into 2009. But the Chicago-based company said Friday it would no longer spend tens of millions of its own dollars making planes that may never be sold just to keep the supply lines open in hopes of new business.

If more planes aren’t ordered, Boeing said the first to lose jobs would be 1,000 workers in St. Louis, 600 in Macon, Ga., and 200 in Mesa, Ariz. The company could not say when those cuts would begin.