An investigation is underway after a Boeing 737 MAX 8 aircraft crashed Sunday in Ethiopia, killing all 157 people on board.
It is the second time in less than six months that one of the planes has crashed within minutes of takeoff, after a new Lion Air Boeing 737 MAX 8 flight went down over the Java Sea last October, killing 189 people.
Both crashes are under investigation and there is no evidence of a link between the two, but similarities between the incidents have prompted caution among some aviation authorities and airlines.
There are approximately 350 Boeing 737 Max 8 aircraft in operation worldwide, being flown by 54 operators, according to the US Federal Aviation Administration (FAA).
Travelers can check the full list of airlines that fly the plane on the Boeing website.
Read on to find out which airlines and aviation authorities have grounded Boeing 737 MAX 8 aircraft, and which will continue to fly the planes.
Who is grounding planes?
The carrier has grounded the remaining four Boeing 737 MAX 8s in its fleet until further notice, as an "extra safety precaution."
Cayman Airways operates two new Boeing 737 MAX 8 aircraft. It said Monday it was grounding both planes "until more information is received."
Who is still flying Boeing 737 MAX 8s?
The US carrier has 24 737 MAX 8 aircraft in its fleet and says it has no plans to ground them at the moment.
In a statement, American Airlines expressed its condolences to the families of those killed, and said it would 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," read the statement. "We have full confidence in the aircraft and our crew members, who are the best and most experienced in the industry."
The US carrier has 34 of the aircraft in its fleet and says it does not plan to change its operational policies or procedures.
"We remain confident in the safety and airworthiness of our fleet of more than 750 Boeing aircraft," read a statement from the airline.
Norwegian will continue to operate its 18 737 MAX 8 aircraft as normal, according to Tomas Hesthammer, Director of Flight Operations.
"We are in close dialogue with Boeing and follow their and the aviation authorities' instructions and recommendations," Hesthammer said in a statement. "Our passengers' safety is and will always be our top priority."
TUI Aviation has 15 of the aircraft in its fleet.
"We do not comment on any speculation and we are, as always, in close contact with the manufacturer," reads a statement from the airline. "We have no indication that we can't operate our 737 MAX in a safe way like we do with all other planes in our network."
SilkAir says it has no plans to ground its six 737 MAX 8 aircraft, which operate between Bengaluru, Cairns, Chongqing, Darwin, Hiroshima, Hyderabad, Kathmandu, Kuala Lumpur, Penang Phnom Penh, Phuket and Wuhan.
"At this point SilkAir's 737 MAX 8 flights are operating as scheduled," says a statement from the airline, which has a further 31 of the aircraft on order.
Fiji Airways currently flies two 737 MAX 8 aircraft and has three on order for 2019. "We have full confidence in the airworthiness of our entire fleet," the airline said in a statement.
Icelandair says it flies three Boeing 737 MAX aircraft, which have not been involved in any incidents.
"At this stage, Icelandair is not taking any action following recent events, but we will, however, follow any developments closely and continue to do all we can to ensure safety on board now as before," the airline said in a statement.
Flydubai operates 11 Boeing 737 MAX 8s, and says it "remain(s) confident in the airworthiness of our fleet."
"We are monitoring the situation and continue to be in touch with Boeing... The safety of our passengers and crew is our first priority," the airline said in a statement.
"The aviation sector is highly regulated and Flydubai rigorously adheres to all regulations," it added.
Canadian airline WestJet says it has 13 MAX 8 aircraft and a total of 121 Boeing 737s in its fleet.
"We are monitoring the situation closely and will not speculate on the cause of the incident," the airline said in a statement. "WestJet remains confident in the safety of our Boeing 737 fleet including our 13 MAX-8 aircraft first introduced in 2017."
GOL Linhas Aéreas
The Brazilian airline has seven 737 MAX 8s in its fleet, part of a total 121 Boeing aircraft.
"GOL continues to follow the investigations and maintains close contact with Boeing for clarification," said the airline in a statement.
"The company reiterates confidence in the safety of its fleet."
What aviation authorities are saying
Civil Aviation Administration of China
China operates 97 of the planes, according to state-run media. In the wake of Sunday's crash, the country's Civil Aviation Administration ordered all domestic 737 MAX 8 jets out of the air by 6 p.m. local time Monday, citing "zero tolerance for safety hazards."
Indonesia temporarily grounded all Boeing 737 MAX 8 on Monday, pending further inspections.
In a statement, the Directorate General of Air Transportation at the Ministry of Transportation said the policy would "ensure that aircraft operating in Indonesia are in an airworthy condition."
Federal Aviation Administration (FAA)
On Sunday, the US aviation authority said it would help Ethiopian authorities investigate the crash.
Following the Lion Air crash involving a 737 MAX 8 in October, the FAA said it had "sent out an emergency Airworthiness Directive to advise carriers and pilots on training to disengage the aircraft's automated controls if there are anomalies."
UK Civil Aviation Authority
"There are currently five Boeing 737 Max 8 aircraft registered and operational in the United Kingdom," a spokesperson for the UK Civil Aviation Authority said, adding that a sixth aircraft is due to enter operation this week.
"The US Federal Aviation Administration (FAA) is responsible for certifying all Boeing 737 Max 8 models and it is the European Aviation Safety Agency (EASA) that validates this certification across the EU, including the UK," said the spokesperson, who said that the CAA is working closely with the EASA.
European Union Aviation Safety Agency (EASA)
EASA said it was monitoring the crash investigation closely.
"We will immediately publish any further information on our website as the necessary information is available," a statement from the agency read.