Why is the 737 max 7 not certified?

The LEAP-1B nacelle inlet is de-iced with hot bleed air. In dry air, with the system running and no water droplets to absorb the heat, the composite inner barrel of the inlet can overheat. The concern is structural: a failed inlet could shed material into the fuselage, potentially at a cabin window. Nothing of the sort has happened in service, but certification asks whether it can happen, and today the answer is yes unless the crew limits how long the system stays on.

For the MAX 8s and MAX 9s already flying, the FAA and Boeing addressed it procedurally: crews must not leave engine anti-ice on for more than five minutes in dry conditions. That is acceptable as an interim measure on an aircraft already certified. For a new variant the standard is stricter, because an aeroplane cannot be approved when its safety margin depends on a pilot remembering a timer. Boeing therefore needs a redesigned inlet, work it has been pursuing since withdrawing its exemption request in January 2024, in the political climate that followed the Alaska Airlines door-plug failure.

Southwest, the launch customer, ordered the MAX 7 to replace its 737-700 fleet and has rebuilt its capacity plans repeatedly, converting orders to the MAX 8 to keep deliveries arriving. Boeing carries an order book it cannot fulfil and a certification team occupied for years longer than planned. The MAX 10, queued behind the MAX 7 and dependent on the same inlet redesign, waits on the outcome as well.