Malaysia is the latest country to temporarily ban Boeing 737 Max aircraft from flying to and from the country, joining Singapore, China and Australia.
The decision comes after an Ethiopian Airlines Boeing Max 8 crashed on Sunday, killing 157 people on board.
It was the second fatal accident involving that model in less than five months.
Singapore's Changi Airport is the world's sixth busiest and a major hub connecting Asia to Europe and the US.
But only a handful of airlines operate Max aircraft in and out of the country.
No Australian airlines operate the Boeing 737 Max, and only two foreign airlines - SilkAir and Fiji Airways - fly the model into the country.
Shane Carmody, who is in charge of aviation safety at Australia's Civil Aviation Safety Authority, said the suspension would remain in place while the organisation awaited "for more information to review the safety risks".
Several airlines and regulators around the world have already grounded the Max 8 model following the crash.
South Korea has asked Eastar Jet, the only airline in the country to own Max 8s, to ground its planes from Wednesday, while Malaysia has banned the jets from its airspace, according to the AFP news agency.
Singapore's aviation authority said the affected airlines include SilkAir, which operates six Boeing 737 Max 8 aircraft, as well as China Southern Airlines, Garuda Indonesia, Shandong Airlines and Thai Lion Air.
In the US, the country's Federal Aviation Administration (FAA) told airlines on Monday it believes Boeing's 737 Max 8 model to be airworthy, despite the two fatal crashes.
Southwest, which has the largest fleet of 737s in the US, said it was offering customers booked on flights using the jet the chance to change their reservation, but would not be offering refunds.
Rival American Airlines said its "standard policies for changes still apply".
What is a Boeing 737 Max aircraft?
The Boeing 737 Max fleet of aircraft are the latest in the company's successful 737 line. The group includes the Max 7, 8, 9 and 10 models.
By the end of January, Boeing had delivered 350 of the Max 8 model out of 5,011 orders. A small number of Max 9s are also operating.
The Max 7 and 10 models, not yet delivered, are due for roll-out in the next few years.
The Max 8 that crashed on Sunday was one of 30 ordered as part of Ethiopian Airlines' expansion. It underwent a "rigorous first check maintenance" on 4 February, the airline said.
Following last October's Lion Air crash in Indonesia, investigators said the pilots had appeared to struggle with an automated system designed to keep the plane from stalling, a new feature of the jet.
It is not yet clear whether the anti-stall system was the cause of Sunday's crash. Aviation experts say other technical issues or human error cannot be discounted.
Eyewitnesses say they saw a trail of smoke, sparks and debris as the plane nosedived.
What have US authorities said?
US aviation officials have said the 737 Max 8 is airworthy and that it is too early to reach any conclusions or take any action.
Boeing has confirmed that for the past few months it has been developing a "flight control software enhancement" for the aircraft.
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Paul Hudson, the president of FlyersRights.org and a member of the FAA Aviation Rulemaking Advisory Committee, nonetheless called for the plane to be grounded.
"The FAA's 'wait and see' attitude risks lives as well as the safety reputation of the US aviation industry," Mr Hudson said in a statement on Monday.
Which UK carriers are flying 737 Max aircraft?
Both TUI and Norwegian say they will continue to operate 737 Max planes in and out of the UK.
Norwegian used the aircraft on morning flights to Oslo and Helsinki on Tuesday.
TUI said its five 737 Max 8s were flying from Manchester to various locations.
But there was no information about flights beyond today.
Can I ask to fly on a different plane?
Some passengers scheduled to fly on a Boeing 737 Max 8 aircraft may wish to transfer to a different flight, but they will have no rights to do so without incurring extra costs under the current regulations.
With regulators in the US declaring these planes safe and flights continuing in the UK and Europe, wary passengers would have to buy a ticket for a different flight and would have no right to a refund, according to consumer group Which?. Any pay-out from travel insurance policies would also be extremely unlikely.
Some airlines are grounding particular planes, but still running scheduled flights on alternative aircraft.
If airlines with these planes do cancel flights, passengers would have the same rights to refunds or re-routing to their destination as they normally do when any flight is cancelled for whatever reason.
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