US authorities set to rule Boeing 737 MAX 8 aircraft are safe to fly

The US government will inform all international airlines it believes the Boeing 737 MAX 8 is airworthy and safe to fly, but is poised to respond if any faults are found.

In a statement, officials say they will "take immediate action" if regulators identify any safety issue, following the fatal crash in Ethiopia on Sunday (local time).

The US Federal Aviation Administration said it will issue a 'Continued Airworthiness Notification' on Monday evening (local time), essentially ruling the aircraft is safe to fly.

"If the FAA identifies an issue that affects safety, the department will take immediate and appropriate action," US Transportation Secretary Elaine Chao said at a press conference. 

"I want people to be assured that we take these incidents, these accidents very seriously."

Canada has taken a similar approach and its transport minister said he will not hesitate to act once the cause of the crash is known.

The safety concerns follow the Ethiopian Airlines crash that killed all 157 people onboard and a Lion Air flight that went down in Indonesia in October, killing 189 people. Both accidents involved a Boeing 737 MAX 8.

The National Transportation Safety Board and the FAA are both in Ethiopia assisting with the investigation.

Boeing's share price dropped 10 percent in early trading on Monday at the prospect that two such crashes in such a short time could reveal flaws in its new plane. 

China has ordered its airlines to ground the jet, a move followed by Indonesia and Ethiopia. Other airlines, from North America, Europe, the Middle East and Fiji, have kept flying the 737 MAX 8 after Boeing said it was safe.