Updated at 5:17 p.m. ET

The Boeing 737 Max is the fastest-selling plane in the company's history. And now it's under immense global scrutiny after the plane has been involved in two deadly crashes soon after takeoff in less than five months.

Boeing has pinned high hopes on the 737 Max. "We expect 737 Max to account for approximately 90 percent of total 737 deliveries in 2019," the company's chief financial officer, Gregory Smith, said in January. "In all, [Boeing] is expected to deliver between 895 and 905 airplanes for the full year."

So far, the manufacturer says it has received more than 5,000 orders for the fuel-efficient plane from more than 100 customers worldwide. The 737 Max has been key to its competition with top rival Airbus, which has found success with a similar model.

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One of the biggest attractions for the airlines that have been lining up to order the 737 Max is that it will save them money, analysts say.

"It's all about the fuel [economy], really," said aviation analyst Richard Aboulafia of the Teal Group. "You're talking about double-digit savings relative to the previous generation."

China and Indonesia are among the biggest users of these new Boeing jets, according to several reports.

Officials in China, Indonesia and Ethiopia have grounded 737 Max aircraft in their countries after Ethiopian Airlines Flight 302 crashed Sunday. The plane crashed shortly after takeoff from Addis Ababa, killing all 157 people on board.

Sunday's disaster followed the crash of a 737 Max flown by Lion Air off the coast of Indonesia in October, killing 189 people.

The planes in both crashes had been recently delivered Boeing 737 Max 8 aircraft.

Three U.S. airlines fly the 737 Max, and all of them said they have no plans to ground the plane. Southwest has 34 of them in its fleet, American has 24 and United has 14.

Boeing stock closed down about 5.3 percent Monday.

Aboulafia, the analyst, said the crashes are not likely to cause a sudden change in Boeing's sales since the planes are ordered years in advance.

"It's a very long sales cycle, and no one's going to cancel their orders and no one's going to make snap judgments on the basis of just this incident," he said.

NPR's Camila Domonoske contributed to this report.

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