US President-elect Donald Trump has tweeted about the "tremendous cost and cost overruns of the Lockheed Martin F-35", causing the aerospace company's stocks to fall on Thursday (22 December). The tweet comes after Trump met with the CEOs of the company as well as Boeing.

It is not the first time Trump has caused trouble for Lockheed, tweeting earlier in December that the F-35 programme and cost was "out of control" and that "billions of dollars can and will be saved on military (and other) purchases after January 20th", the date of his inauguration.

In Thursday's comment, Trump added that he has asked Boeing to "price-out a comparable F-18 Super Hornet". The president-elect has caused similar problems for Boeing before when he tweeted on 6 December that the cost of the new Air Force One was "more than $4bn. Cancel Order!"

Soon after the tweet, CNBC reported that Lockheed Martin's shares had fallen 1.7% while Boeing shares had risen 0.6%.

Lockheed Martin is currently in negotiations with the US government for the next 100 F-35 fighters. It has been suggested that the F-35 and F-18 are not comparable as the F-35 is "stealthy" while the F-18 is not.

CNBC reported that the one tweet took away around $1.2bn (£976m) from Lockheed Martin's market value.