What happened with the 737 MAX?

The 737 MAX carries CFM LEAP-1B engines that are larger and mounted further forward than those of the 737NG, which alters pitch behavior at high angles of attack. To make it fly like its predecessor without requiring extra pilot training, Boeing added MCAS, software that pushes the nose down on its own. It relied on a single angle-of-attack sensor and wasn't documented in the manuals. On 29 October 2018, Lion Air flight 610 crashed into the Java Sea with 189 people aboard; on 10 March 2019, Ethiopian Airlines flight 302 crashed shortly after takeoff from Addis Ababa with 157 aboard. In both cases a faulty sensor reading triggered MCAS repeatedly.

China was the first to ban the model, and within days EASA and the FAA followed: the 387 delivered aircraft were grounded from 13 March 2019. Boeing redesigned MCAS to use two sensors, act only once and remain overridable by pilots, and the FAA lifted the ban on 18 November 2020 with mandatory simulator training. Boeing paid $2.5 billion in a settlement with the Department of Justice for having misled regulators.

On 5 January 2024, an Alaska Airlines 737 MAX 9 lost a door plug at 4,900 m (16,000 ft) with no fatalities. The NTSB found that the four retaining bolts were missing after factory work. The FAA capped production at 38 aircraft a month; the CEO stepped down and the manufacturer overhauled its quality control. Despite it all, the MAX continues to attract orders (as of September 2026).