The crisis facing aviation giant Boeing intensified this week as 737 Max 8 aircraft were grounded around the world following the deadly Ethiopian Airlines crash on Sunday. President Donald Trump issued an emergency order following suit on Wednesday afternoon as they were banned by almost every other country in the world.

The New York Times previously tallied up the grounding orders and concluded the United States was “basically alone” in allowing 737 Max 8s to fly after Canada grounded them on Wednesday morning. Canadian authorities said they would not even allow 737 Max 8 and Max 9 planes from the U.S. to pass through their airspace. Canada’s transport minister said the decision was made based on “new data” about the Ethiopian Airlines crash received on Wednesday morning.

The European Union and India grounded 737 Max aircraft on Tuesday.

China, which owns about a quarter of the operational 737 Max aircraft in the world, suspended flights on Monday, an announcement that apparently inspired carriers across Asia and the Middle East to follow suit. NPR on Tuesday published a list of 29 countries that have grounded the Boeing planes, a list that did not yet include Canada.

The Canadian and Chinese grounding orders were especially momentous because their civil aviation authorities rarely disagree with the American Federal Aviation Administration (FAA). Chinese officials reportedly consulted with the FAA before making their decision, but then declared the American agency is having “difficulty making a decision, so we took the lead.” China indicated it will allow 737 Max flights to resume once Boeing provides sufficient safety guarantees.

The FAA stated on Tuesday that will continue to “review extensively all available data and aggregate safety performance from operators and pilots of the Boeing 737 Max.”

“Thus far, our review shows no systemic performance issues and provides no basis to order grounding the aircraft. Nor have other civil aviation authorities provided data to us that would warrant action,” the FAA wrote.

The agency promised to take “immediate and appropriate action” if any defects in the aircraft are identified.

On Monday, the FAA ordered a series of design changes to the 737 Max line based on the investigation of a previous crash in Indonesia, including revised safety checklists, new training requirements, and “changes to the software that forces the nose down in certain situations to prevent an aerodynamic stall.” The order will go into effect next month. Boeing representatives said a “software enhancement” to the flight controls is already under development.

The Hill reported on Tuesday that while Boeing CEO Dennis Muilenburg gave President Donald Trump assurances the company’s planes are safe to fly, and the administration wanted to give the FAA more time to review the situation, pressure for immediate action is mounting both internationally and domestically:

Sen. Ted Cruz (R-Texas,) chairman of a Senate subcommittee on aviation and space, urged the U.S. government to ground the planes “until the FAA confirms the safety of these aircraft & their passengers.” “Further investigation may reveal that mechanical issues were not the cause, but until that time, our first priority must be the safety of the flying public,” he said in a tweet. “I intend to hold a hearing to investigate these crashes, determine their contributing factors, and ensure that the United States aviation industry remains the safest in the world.” Sen. Dianne Feinstein (D-Calif.) called on Elwell to ground the aircraft, while Sen. Richard Blumenthal (D-Conn.) said American Airlines, Southwest Airlines and United Airlines should voluntarily suspend use of the 737 Max models “until we have answers.” Sen. Mitt Romney (R-Utah) and Rep. Sheila Jackson Lee (D-Texas) were among those who called on the FAA to ground the planes pending an investigation into the causes of recent crashes.

Senator Elizabeth Warren, a Democrat running for her party’s presidential nomination in 2020, made it personal, political, and conspiratorial by demanding congressional hearings on “whether an administration that famously refused to stand up to Saudi Arabia to protect foreign arms sales has once again put lives at risk for the same reason.”

The Hill queried the top U.S. carriers that employ Boeing planes and found Southwest Airlines has 34 of the 737 Max 8 planes, American Airlines has 24, and United Airlines has 14 Max 9 models. All three of the airlines said they are working closely with the FAA and Boeing and are confident the planes are safe to fly.

The two major flight attendants’ unions, on the other hand, expressed concerns about the safety of the planes and demanded FAA action to restore public confidence. One of the unions implied its members might not be willing to fly on 737 Max 8 planes if their concerns are not addressed.

The Dallas Morning News reported on Tuesday that pilots have filed numerous complaints about the Max 8 with the FAA. The article cited five complaints filed in October and November related to the autopilot system, several of them noting that the plane suddenly nosed down on its own. Investigators believe this type of behavior was a factor in both the Indonesian and Ethiopian crashes, although the investigations are still ongoing.

Ethiopian Airlines CEO Tewolde GebreMariam told CNN on Tuesday that his pilot encountered “difficulties with the flight control of the airplane” and requested permission to return to base before the crash, which killed all 157 people aboard. GebreMariam stated Ethiopian Airlines pilots were given additional training on the 737 Max 8 after the Indonesian crash in October.

According to the Dallas Morning News, a total of 18 carriers have expressed confidence in the safety of the planes and decided not to voluntarily ground them.