A day after the second deadly crash since October of a popular new plane model, countries and airlines began grounding flights of the Boeing 737 Max 8. By the afternoon of the third day, U.S. carriers were the only major operators still flying the planes, and President Trump announced that those flights would be grounded as well.

All 157 people aboard Ethiopian Airlines Flight 302 were killed near Bishoftu, Ethiopia, on March 10 after a six-minute flight in which the jet’s altitude and airspeed climbed and dipped erratically.

More than 8,800 flights of the 737 Max 8s (and similar Max 9s) occur around the world in a typical week. These latest versions of the popular 737 have more fuel-efficient engines than their predecessors, and Boeing hopes the new line will compete successfully with European rival Airbus.

Roughly 60 airlines operate at least one of these planes, which debuted in 2017, and thousands more have been ordered. Worldwide, 427 of the planes have been allocated so far, 76 to U.S. airlines Southwest (34), American (26) and United (16), according to a compilation by Flightradar24. Not all allocated planes are flying routes yet.