NEW YORK -- Shares of Lockheed Martin fell Monday, wiping out nearly $2 billion of the company's market value, as President-elect Donald Trump tweeted that making F-35 fighter planes is too costly and that he will cut "billions" in costs for military purchases.

Trump didn't mention any specific company in his tweet, but Bethesda, Maryland-based Lockheed makes the F-35 one-seat fighter aircraft and is a major U.S. defence contractor.

The F-35 program made up 20 per cent of Lockheed's total 2015 revenue of $46.1 billion. And U.S. government orders made up 78 per cent of its revenue last year. The F-35 program directly or indirectly supports more than 146,000 U.S. jobs, according to the company's website.

In a statement Monday, Lockheed said that it has worked to lower the price of the F-35 by more than 60 per cent and said it expects the aircraft to cost $85 million in 2019 and 2020.

"We welcome the opportunity to address any questions the president-elect has about the program," said Jeff Babione, general manager of the F-35 program. "It's an amazing program."

This is the second time in a week that Trump has blasted U.S. aircraft spending. Trump tweeted last week that costs to build new presidential planes by Boeing Corp. were "out of control" and ended the tweet with "Cancel order!

Lockheed Martin Corp. shares fell $6.36, or 2.5 per cent, to $253.17 in afternoon trading Monday.

Shares of other defence contractors also tumbled. Raytheon Co. dropped 2.2 per cent to $143.08 and Northrop Grumman Corp. which fell 3.4 per cent to $230.