The newest version of Boeing’s most popular jet is again under scrutiny after the deadly crash in Ethiopia on Sunday, leading airlines around the world to ground their fleets of 737 Max aircraft.

On Monday morning, MIAT Mongolian Airlines ordered that its newly leased Boeing 737 Max 8 be withdrawn from service pending an investigation. MIAT has recently expanded its fleet by leasing two 737 Max aircraft from the global leasing company Avolon. The first of the planes arrived on 1 February.

In October, the same model crashed in Indonesia, killing 189 people. In both cases, brand-new planes faltered minutes after takeoff and plunged into a deadly descent, leaving no survivors.

The investigation into both cases is continuing, but the latest crash renewed questions about the safety of the 737 Max, which Boeing unveiled in 2017 and sold as a fuel-efficient, technologically advanced upgrade to its popular 737.