Ethiopian Airlines Flight ET302 is the second catastrophic crash of a nearly brand-new Boeing 737 MAX airliner in four months.

Regulatory agencies in China, the United Kingdom, Australia, Singapore, Indonesia, and Ethiopia have all grounded the 737 MAXs operating within their jurisdiction.

Airlines including Norwegian Air, AeroMexico , Jet Airways, and Gol have also grounded their MAX fleets.

AeroMexico The Boeing 737 program represents 80% of Boeing's order backlog.

The crash of Ethiopian Airlines Flight ET302 has raised alarm bells across the airline industry. The incident, which killed all 157 passengers and crew aboard the plane, is the second catastrophic crash of a nearly brand-new Boeing 737 MAX airliner in four months.

Regulatory agencies in China, the United Kingdom, Australia, Singapore, Indonesia, and Ethiopia have all grounded the 737 MAXs operating within their jurisdiction.

Airlines including Norwegian Air, AeroMexico, Jet Airways, and Gol have also grounded their MAX fleets.

Read more: Two Boeing 737 MAX airliners have crashed since October — here are the airlines that fly the plane.

It's a stunning turn of events for the best selling commercial airliner of all time.

Since the 1960s, the US industrial giant has taken sold 15,000 of the single-aisle jet.

The latest version of the plane dubbed the 737 MAX, is the fastest selling version of the series, racking up roughly 5,000 orders.

The plane entered service in 2017.

The significance of the 737-program to Boeing cannot be overstated.

Boeing Commercial Airplanes, the company's airliner division, has a backlog 5,870 planes valued at more than $400 billion.

As it currently stands, the 4,699 yet-to-be-delivered 737s represent 80% of that backlog.

The 737 MAX is currently built alongside the previous generation 737NG (Boeing 737-600,700,800, and 900) at Boeing's Renton, Washington factory.

By the end of 2018, Boeing ramped up production of the 737 to 52 aircraft a month. This year, it plans to produce 57 a month.

Last year, Boeing delivered 256 MAX aircraft to customers, representing nearly half of all 737 deliveries.

As production of the NG comes to an end, the MAX will be asked the carry the load for the 737 program.