The deal should keep things humming at the sprawling plant in Long Beach, California through 2014, Boeing spokesman Jerry Drelling said in a Los Angeles Times report.
Drelling said the order "helps us keep the line alive and supports jobs".
Boeing is the largest employer in Long Beach near Los Angeles.
The plane has an estimated $5.8 billion annual economic impact and the jobs of about 25,000 workers in 44 states depend on it, Drelling said.
India on Monday gave its go ahead to purchase 10 C-17 heavy-lift military aircraft in a deal worth $4.1 billion.
The deal with Boeing is the biggest defence deal between India and the US.
"We are still waiting on the signatures, but the deal is 99.9 per cent done," the LA Times report quoted Stan Klemchuk, president of the United Aerospace Workers Local 148, which represents 1,600
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