About half of the 350 Boeing 737 MAX 8 passenger jet airliners currently in operation have now apparently been grounded as a precaution in the wake of the horrific crash of an Ethiopian Airlines plane of this type on Sunday.

These 350 planes are operated by 54 airlines, according to the U.S. Federal Aviation Administration (FAA). Some 4,600 737 MAX 8s are on order.

Yesterday, China, Ethiopia and the British overseas territory of the Cayman Islands became the first places in the world to ban their airlines from flying the new Boeing 737 MAX 8 narrow-body jetliner. They have since been joined by at least 14 airlines from around the world. This list is incomplete since not all the airlines in China operating this aircraft have been listed.

China is the largest single country that operates the 737 MAX 8. Various domestic airlines fly 97 of these planes, or almost a third of those in service.

The partial list of airlines that have temporarily grounded their 737 MAX 8ss are: Aeromexico, Aerolíneas Argentinas, Cayman Airways, Comair Airways, Ethiopian Airlines, Garuda Indonesia, Shandong Airlines, Thai Lion Air, SilkAir, China Southern Airlines, China Eastern Airlines, Air China, and Hainan Airlines.

Not a single United States airline has grounded its 737 MAX 8s, placing them at odds with the rest of the world. An investigation is underway as to why a Boeing 737 MAX 8 aircraft crashed in Ethiopia, killing all 157 people on board.

Some of the airlines still flying the beclouded plane are American Airlines, Southwest Airlines, Norwegian Airlines, TUI, Fiji Airways, Icelandair, Flydubai, WestJet and GOL Linhas Aéreas.

American Airlines said it will continue to monitor the investigation into the crash.

"At this time there are no facts on the cause of the accident other than news reports," said American Airlines in a statement. "We have full confidence in the aircraft and our crew members, who are the best and most experienced in the industry."

The FAA has also released an international notice promising to "take immediate and appropriate action" should safety issues be identified in the fleet.

"Today, the FAA will issue a Continued Airworthiness Notification to the International Community (CANIC) for Boeing 737 MAX operators. The FAA continuously assesses and oversees the safety performance of U.S. commercial aircraft. If we identify an issue that affects safety, the FAA will take immediate and appropriate action."

It‘s the second time in about five months that one of the planes has crashed within minutes of takeoff. In October 2018, a new Lion Air Boeing 737 MAX 8 flight smashed into the Java Sea last October, killing 189 people.

Boeing 737 MAX 8
An American Airlines Boeing 737 Max 8, on a flight from Miami to New York City, prepares to land. American Airlines still flies the Max 8 despite the crash of a similar aircraft in Ethiopika on March 10 that killed all onboard. Drew Angerer/Getty Images

Both crashes are under investigation and there is as yet no evidence of a link between both crashes. But there are similarities in both these horrific incidents, and it is this circumstantial evidence that apparently prompted many airlines to ground their 737 MAX 8s out of an abundance of caution.

The 737 series is the best-selling commercial jetliner in history. The 737 has been in continuous production since 1967. The 10,000th 737 rolled-out on March 13, 2018, and this was a MAX 8 destined for Southwest Airlines.