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Boeing Co. said Tuesday the first test flight of its long-delayed 787 jetliner has been postponed until next year due to an eight-week strike by union workers.

The Chicago-based airplane maker had scheduled the inaugural flight of the next-generation passenger jet - delayed four times already - for the fourth quarter of this year.

But Boeing spokesman Jim Proulx said the strike, which started Sept. 6 and forced the company to temporarily shut its commercial aircraft business, had pushed back the test flight to an unspecified time next year.

"Given the duration of the ... work stoppage, first flight of the 787 will not be accomplished in the fourth quarter 2008," he said. "The time frame for first flight has not been established and will be based on the strike recovery assessment."

The postponement was the latest of several delays of the hot-selling 787, which is expected to provide high fuel efficiency because of its construction from lightweight carbon composite parts.

Even before the strike, the highly anticipated airplane had been hampered by lengthy delays caused by production glitches partly due to a reliance on overseas suppliers. The company has lost credibility, and billions of dollars in expected additional costs and penalties, with the delays leaving the 787 more than a year behind the original schedule.

Boeing, which also produces 737, 747, 767 and 777 jetliners, postponed 787 test flights in September and October of 2007 and January and April of this year.