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.

The 737 Max became the fastest-selling plane in Boeing history, the company said on its website, and is used by airlines around the world.

Here’s what we know so far about the plane involved.

What is the Boeing 737 Max?

It is the latest generation of the Boeing 737, a kind of aircraft that’s been flying since the 1960s. There are four kinds of Maxes in the fleet, numbered 7, 8, 9 and 10. The 8 series, which was involved in the crashes in Indonesia and Ethiopia, has been flying the longest.

The 737 Max is mostly used for short- and medium-distance flights, but a few airlines fly it between Northern Europe and the East Coast of the United States. It is more fuel efficient and has a longer range than earlier versions of the 737.

The flight on Sunday was traveling from the Ethiopian capital, Addis Ababa, to Nairobi, Kenya.

What is known after the crash in Indonesia?

It was too soon to tell on Sunday whether the causes of the Ethiopian Airlines crash were the same as or similar to those of the Lion Air crash in Indonesia last year.