Shares of Lockheed Martin Corp. LMT, -1.33% slumped 2.7% in premarket trade Monday, after President-elect Donald Trump called out the defense contractor, saying in tweet that the F-35 stealth fighter program's cost is "out of control." Trump said Monday that "billions of dollars can and will be saved on military (and other) purchases" after he is inaugurated on Jan. "20. In an interview on Fox News Sunday," Trump repeated his doubts after the F-35 jet being built by Lockheed, adding that government procurement officials should be barred for life for working for defense contractors. Trump's tweet about Lockheed follows a similar tweet about Boeing Co. BA, -3.58% last week, in which he said the order to build new Air Force One planes should be canceled because of spiraling costs. The company and the White House disputed Trump's claims about the costs. Lockheed's stock has run up 8.5% since the election through Friday, while the S&P 500 SPX, -2.37% has gained 5.6%.