Crain's Chicago Business reported Wednesday the job cuts are part of the airline's plan to lay off 7,000 workers, or about 13 percent of its work force. The company is grounding 100 older Boeing 737s and reducing its capacity to help cut maintenance and fuel costs.

The cuts, announced in July, had been expected to take place by the end of 2009, the newspaper reported.

About 680 of United's mechanics are expected to be laid off Jan. 11, including about 150 at O'Hare International Airport in Chicago. More than 200 of the layoffs will come from United's primary maintenance facility at San Francisco International Airport.

Additionally, United is eliminating maintenance operations at Newark, LaGuardia and Philadelphia airports, the source said.