Thursday is a day of closure for Boeing (BA) and the city of Long Beach, Calif., as the company delivers its 223rd and final C-17 to the U.S. Air Force there.

Boeing is winding down its program for the massive cargo jet, which is expected to shut down completely by late next year. That ending also calls into question the fate of the 1.1 million-square-foot Boeing plant in Long Beach -- one of the last remaining aircraft factories in Southern California -- and the estimated 4,000 workers employed there.

Plans for the C-17 cargo jet, known as both the Globemaster and the T-1, began during the Cold War. Design of the massive plane which can carry tanks, heavy machinery, tons of equipment, scores of troops or even be converted into a mobile hospital, began in the 1980s with McDonnell Douglas. Boeing inherited the program when it merged with McDonnell Douglas in 1997.

Since then, the C-17 -- with its relatively short takeoff and landing requirements -- has become a workhorse for both the U.S. Air Force and its allies, while reportedly generating more than 30,000 jobs in 44 states with an estimated total economic impact of $5.8 billion.

After the C-17's final domestic delivery to the Air Force's 437th Airlift Wing at Joint Base Charleston, S.C., Boeing will concentrate on the remaining overseas orders for the plane. A current order from India for 10 C-17s, according to The San Gabriel Valley Tribune, will keep the Long Beach plant busy until the third quarter of next year.

The Los Angeles Times says Boeing, which has already cut jobs and slowed down production rates in Long Beach, has been trying to buy time for the plant with the international sales.

"We've known this was coming for a while," Long Beach Mayor Bob Foster told the newspaper. "I'd love for the Air Force to buy more C-17s, but they have made their decision. The future is going to be in foreign sales."

The Tribune, meanwhile, reports aerospace jobs in Los Angeles County, once an economic engine for the U.S. aviation industry, have dropped from more than 130,000 in 1990 to about 38,000 last year.