But September has been the new target for several months running — Musk said "two months" back in July — and the company seems very confident that it'll arrive on schedule. That's not to say there aren't challenges; Tesla says unforeseen issues with even a single supplier, should any arise, "could reduce Model X production by approximately 800 units for the quarter." The automaker is also cautioning that any Model X production difficulties could potentially slow the rate at which Model S vehicles leave the assembly line. “The Model X is a particularly hard car to build. Maybe the hardest car in the world to build," Musk said during Tesla's earnings call later in the afternoon. But he seems largely unfazed. "I think it’s going to blow people away."