Canada is grounding all of its Boeing 737 Max 8 aircraft and banning the jet from entering its airspace until further notice as safety concerns continue to mount following two deadly crashes.

"This safety notice restricts commercial passenger flights from any air operator, both domestic and foreign, of the Boeing 737 Max 8 and 9 aircraft from arriving, departing, or overflying Canadian airspace," Transport Minister Marc Garneau told reporters earlier today. (The Max 9 has an extended fuselage, but uses the same systems as the Max 8s).

Canada had been one of the last holdouts on temporarily banning the Max 8s in the wake of the recent Ethiopian Airlines crash that killed all 157 people on board, including 18 Canadians. The U.K., the European Union, Australia and other countries had moved already to ban the jet from their airspace in response to growing safety concerns.

Garneau said the decision to issue the safety notice was made after his department received new data suggesting a similarity between the Ethiopian Airlines crash and another deadly crash near Indonesia in October.

The minister said much of the new information is new and unproven, but added:

"There are — and I hasten to say not conclusive — but there are similarities that sort of exceed a certain threshold in our minds with respect to the possible cause of what happened in Ethiopia"

"My departmental officials continue to monitor the situation and I will not hesitate to take swift action should we discover any additional safety issues," he said.

U.S. follows suit

U.S. President Donald Trump issued an "emergency order" grounding all Boeing 737 Max 8 and Max 9 a few hours after Canada's decision.

Garneau said Canada alerted the U.S. to the safety notice on Wednesday morning.

According to Reuters, the Federal Aviation Administration held urgent meetings on the issue after Canada announced it would become the latest major country to ground the jets.

According to a source with direct knowledge of the matter, Garneau directly contacted his counterpart, U.S. Secretary of Transportation Elaine Chao. The source said the Americans understood Garneau's decision and did not try to persuade Ottawa to change its mind.

"It was always a possibility, but the fact that they announced it just after us came as a bit of a surprise," said Garneau.

Transport Minister Marc Garneau discusses the decision to ground Boeing 737 Max 8 and 9 aircraft, after Canada had been one of the last holdouts. 9:09

Air Canada, which already had cancelled multiple scheduled flights to and from London in response to the U.K. closing its airspace yesterday, said it's working to rebook passengers.

"Air Canada's cancellation and rebooking policies are in place with full fee waiver for affected customers," said a spokesperson.

"We are working to rebook impacted customers as soon as possible, but given the magnitude of our 737 MAX operations, which on average carry nine to twelve thousand customers per day, customers can expect delays in rebooking and in reaching Air Canada call centres."

WestJet also said it will begin complying with Transport Canada's direction.

"We respect the decision made by Transport Canada and are in the process of grounding the 13 MAX aircraft in our fleet," said the company in an email.

"This decision has an impact on the travel plans of our WestJet guests and we ask for understanding as we work to rebook all guests affected as quickly as possible."

An Air Canada Boeing 737 MAX 8 aircraft is towed in on Wednesday behind another Air Canada Boeing 737 MAX 8 at Toronto's Pearson International Airport. (Chris Helgren/Reuters)

Toronto-based Sunwing Airlines announced late Tuesday it would voluntarily ground its four Boeing 737 Max 8 aircraft for "evolving commercial reasons," such as airspace restrictions imposed by some destinations.

The union representing Air Canada's 8,500 flight attendants welcomed the decision.

"In light of the new data received by the federal government, we welcome the Minister's decision to err on the side of prudence until the analysis of the causes of the Ethiopian Airlines Flight 302 crash is completed," said CUPE spokesperson Wesley Lesosky.

Transport Minister Marc Garneau illustrates the similarities between the Lion Air flight crash from October 2018 to this past weekend's Ethiopian Airlines plane crash out of Addis Ababa. 1:23

Earlier this week, Garneau said it would be "premature" to ground all 41 of the 737 Max 8s currently owned by Canadian air carriers.

However, shortly after the U.K. announced yesterday it is temporarily banning the jets from its airspace, Garneau tweeted that he was cancelling previous plans and meeting with his civil aviation expert panel to discuss the Max 8 aircraft.

Both the Conservatives and the NDP had been calling on the government to ground the planes as a precaution.

Brian Masse, the NDP innovation, science and economic development critic, criticized the speed of Garneau's decision Wednesday, saying "it should have been made sooner" given how other countries took action well before the midday Wednesday announcement.

Masse is asking Garneau to enact a "contingency plan" to ensure passengers who find their travel plans disrupted by the grounding of these aircraft are not "gouged" by airlines during the rebooking process.

"Canadian airlines have the privilege of providing air transport to millions of Canadians and this entails comprehensive responsibilities to ensure their passengers are safe and treated fairly in the market," he wrote in a letter. "Consumers should not be further victimized by predatory practices or pricing during this time."

Pilot reported problems: airline

Sunday's disaster follows another fatal crash of the 737 Max 8 jet in Indonesia five months ago, which killed 189 people and raised concerns about the fleet's automated flight systems.

NDP Leader Jagmeet Singh and Conservative MP Pierre Poilievre both agree that the government should ground the Boeing 737 Max 8 jets until they can be proven to be safe. 0:55

Asrat Begashaw, a spokesperson for Ethiopian Airlines, said that before the crash, the pilot reported flight-control problems and asked to return to Addis Ababa, where the flight to Nairobi originated.

The 'black box' flight recorders from the crash site will be sent to Europe for analysis, he said.