Shares of Lockheed Martin and Boeing made diverging moves in extended trading Thursday after President-elect Donald Trump tweeted about the companies.

Trump said the "tremendous cost and cost overruns" of Lockheed Martin's F-35 program led him to asking Boeing to "price-out a comparable F-18 Super Hornet."

Based on the tremendous cost and cost overruns of the Lockheed Martin F-35, I have asked Boeing to price-out a comparable F-18 Super Hornet! — Donald J. Trump (@realDonaldTrump) December 22, 2016

Lockheed Martin shares fell about 2 percent, while Boeing shares gained about 1 percent. Trump's tweet shaved off about $1.2 billion of Lockheed Martin's market value.

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"We have committed to working with the president-elect and his administration to provide the best capability, deliverability and affordability across all Boeing products and services to meet our national security needs," Boeing told CNBC in a statement.

A spokesman for Lockheed Martin declined to comment to CNBC.

The president-elect previously threatened to cancel the order for a new Air Force One from Boeing because of the costs. He's also criticized the price of Lockheed Martin's F-35 program before, which took as much as $4 billion off of the company's market value.

The tweet comes after Trump met with the CEOs of both companies at his Mar-a-Lago resort in Florida on Wednesday. After meeting with the president-elect, Lockheed Martin CEO Marillyn Hewson said she "appreciated the opportunity to discuss the importance of the F-35 program and the progress we've made in bringing the costs down."