Boeing has put out a press release on Air Force One this morning suggesting they are still just in the discovery phase of its contract with the DOD:

Boeing Statement on Air Force One

CHICAGO, Dec. 6, 2016 /PRNewswire/ — Boeing (NYSE: BA) today issued the following statement regarding the Air Force One program:

“We are currently under contract for $170 million to help determine the capabilities of these complex military aircraft that serve the unique requirements of the President of the United States. We look forward to working with the U.S. Air Force on subsequent phases of the program allowing us to deliver the best planes for the President at the best value for the American taxpayer.”

So it sounds like they aren’t even building it yet. Perhaps they’ve suggested it could cost $4 billion and Trump is using the bully pulpit to drive the price tag down? I don’t know, but there seems to be a rift of information we don’t have between Trump’s tweet and this press release from Boeing.