President-elect Donald Trump upended years of Pentagon procurement planning with a tweet on Thursday, announcing he had asked Boeing Co. to price an upgrade of its F-18 Super Hornet jet that could replace Lockheed Martin Corp.'s F-35, the most expensive U.S. weapon system ever.

"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!" Trump said Thursday in a post on Twitter.

Lockheed's $379 billion F-35 Joint Strike Fighter is intended to be the mainstay fighter of the Air Force, Navy and Marine Corps, replacing several older planes, including Boeing's F-18. Development of the F-35 is more than a decade in the works, and Lockheed is planning to build more than 2,400 of the aircraft for the U.S. and allied air forces, a project that will create tens of thousands of jobs at factories across the country and overseas.