Just one day after signing a huge contract to sell aircraft to China, Boeing (NYSE: BA) said it will lay off about 1,100 U.S, workers involved in the manufacture of its C-17 military-cargo aircraft through the end of next year.

Boeing said it is scaling back production of its C-17 Globemaster III airlifters to 10 per year from the 13 it expected to deliver in 2011.

The bulk of the job losses will occur in Southern California, primarily at facilities in Long Beach.

According to the Long Beach Press Telegram, Boeing has steadily been reducing jobs at its Long Beach site – the company had 20,000 employees there in 1990; and now has only about 7,000.

Ironically, the U.S. government is currently in the midst of preparing an agreement to sell ten C-17s to India for $5.8-billion

Meanwhile, Southern California has seen its once vital aerospace-defense industry wither away.

According to the Los Angeles Times, the industry employed 160,000 people in the region just two decades ago -- now, there are about 48,000.

Our rich history of aerospace manufacturing makes this an emotional day for Long Beach, as the C-17 plant is the last of what was previously a robust aerospace manufacturing industry in California, Long Beach Mayor Bob Foster said.

The Long Beach area has witnessed the closing of many other aircraft manufacturing facilities over the years, including a McDonnell Douglas plant that made MD-80 commercial jets and another Boeing site that made 717 jetliners.