Boeing warns 737 MAX production ramp-up slower, 777X tests slip to 2027, stock drops over 5%

Boeing shares fell on September 16, 2026 after CEO Kelly Ortberg told an investor conference that the company has not yet steadied 737 MAX output at its target rate. "We are not stable yet at 47 a month," Ortberg said, and the stock dropped between 5% and 6% at its intraday lows before closing down 3.68%.

Ortberg pointed at one bottleneck in particular. "Currently, it's wing production that is constraining the company," he said of the Renton line, which is the same wing-assembly constraint Aviation Week had identified as the reason the 47-jet target keeps slipping. Boeing also flagged that its 2026 free-cash-flow outlook is under pressure at the upper end, which it attributes to the slower 737 and 787 rate ramps rather than to any single program event.

The 777X carries its own delay, and it is a separate problem from the cash-flow guidance. Certification work on a GE9X engine seal is expected to push part of the flight-test campaign into 2027. Boeing continues to target the start of 777X deliveries in 2027, so the testing slip compresses the schedule rather than moving the delivery date.

Labor is a contingency rather than a live disruption. Boeing reached a tentative agreement with its SPEEA engineers on September 11 and ratification is still pending; the earliest a walkout could begin is October 7. Ortberg raised it as a risk to production schedules, not as something already happening.

The one clear positive was certification of the 737 MAX 10, which Ortberg described as coming "very soon" with flight testing complete and FAA paperwork the remaining step. For BA, the near-term question is whether wing capacity at Renton can support the 47-per-month rate before the free-cash-flow guidance has to move, with the SPEEA ratification vote and the GE9X seal certification as the two dated events to watch.