Boeing faces a growing crisis of confidence over its 737 Max jet, as regulators and airlines from Singapore to Australia move to ground or block the plane following two deadly crashes in five months.

A day after U.S. regulators stood by the jet’s airworthiness, airlines and aviation authorities from South America to Asia instead opted for a zero-risk approach. Australia followed Singapore in temporarily blocking the 737 Max from its airspace, meaning the newest version of Boeing’s best-selling model is now barred from Asia’s second-busiest international airport and a key long-distance travel destination.

The Civil Aviation Authority of Singapore barred any Boeing 737 Max flight in and out of the city-state. The decision dragged airlines including Singapore Airlines Ltd.’s SilkAir, China Southern Airlines Co., PT Garuda Indonesia and Shandong Airlines Co. into a standoff with the Chicago-based plane maker and the U.S. regulator.

The similarities between Sunday’s disaster in Ethiopia and an October crash in Indonesia, both involving the Boeing 737 Max aircraft, have spooked travelers and sparked worries that the jet is fatally flawed. Despite the U.S. Federal Aviation Administration’s verdict that the plane remains safe to fly, the model was struck by the fresh wave of groundings that could potentially snowball into lost aircraft sales.

“During the temporary suspension, CAAS will gather more information and review the safety risk associated with the continued operation of the Boeing 737 Max aircraft into and out of Singapore,” the authority said.

The announcement follows Max jet groundings by low-cost Brazilian carrier Gol Linhas Aereas Inteligentes SA and Grupo Aeromexico SAB. Hours earlier, the Mexican carrier had said its Max aircraft were in perfect condition.

The spreading cautionary moves are a reaction to the two deadly catastrophes that have eroded faith in the world’s most widely flown jetliner, even after the FAA said there isn’t conclusive evidence so far to link the crashes.

The Ethiopian Airlines jet crashed minutes after takeoff on March 10, killing all 157 people on board. That accident was preceded by a crash of the same model operated by Indonesia’s Lion Air on Oct. 29, in which pilots struggled to maintain control following an equipment malfunction. Chicago-based Boeing is racing to roll out software improvements for the aircraft to help prevent a repeat of the Lion Air crash.

Singapore’s ban on 737 Max aircraft, no matter which carrier is operating the planes, is wider than the freeze put in place Monday by China and Indonesia, which both grounded their airlines’ 737 Max 8 aircraft.

Singapore’s suspension includes both the Max 8 and 9 variants and affects foreign carriers that deploy the aircraft for flights into the island-city, the CAAS said. Singapore is monitoring the situation and is in close contact with Boeing as well as the FAA and other aviation regulators, it said.

The 737 Max is the newest version of Boeing’s most important aircraft type, a plane family that generates almost one-third of the company’s operating profit. The narrow-body jet forms the backbone of many global airline fleets that use the model and Airbus SE’s competing A320 line on shorter routes.