The United States told airlines it was safe to fly Boeing 737 MAX 8 planes as investigators found two black box recorders that will help piece together the final moments of an Ethiopian Airlines crash which killed 157 people.

The announcement came after China and Indonesia grounded all of their fleets citing safety concerns, contributing to a drop in Boeing Co shares that wiped billions of dollars off the market value of the world's biggest plane maker.

Ethiopia’s flag carrier has also suspended use of the aircraft over safety concerns as the east African country marks a day of mourning and authorities search for the remains of victims, including at least nine Britons.

The US Federal Aviation Administration however, issued a "continued airworthiness notification" to assure operators of the plane that it was safe to fly. It said it was collecting data on the crash and keeping in contact with international civil aviation authorities and would take immediate action if it identified any safety issues.

Southwest Airlines Company which operates the largest fleet of 737 MAX 8s, said it remained confident in the safety of all its Boeing planes even as it received a rush of queries from customers wanting to know if they were booked to fly on a 737 MAX 8.

Plane crash kills 157 in Ethiopia Show all 15 1 /15 Plane crash kills 157 in Ethiopia Plane crash kills 157 in Ethiopia People stand near collected debris at the crash site AFP/Getty Plane crash kills 157 in Ethiopia A man carries a piece of debris on his head at the crash site AFP/Getty Plane crash kills 157 in Ethiopia Wreckage lies at the crash site of the Ethiopia Airlines Boeing 737 near Addis Ababa EPA Plane crash kills 157 in Ethiopia Debris at the site of the crash near Addis Ababa Reuters Plane crash kills 157 in Ethiopia CEO of Ethiopia Airlines, Tewolde Gebremariam inspects the crash site AP Plane crash kills 157 in Ethiopia Debris from the crashed aeroplane AP Plane crash kills 157 in Ethiopia UN staff observe a minutes silence for the victims of the plane crash. 19 UN workers were killed in the crash AFP/Getty Plane crash kills 157 in Ethiopia Rescuers work at the scene of the crash near Addis Ababa, Ethiopia AP Plane crash kills 157 in Ethiopia Rescuers work at the scene of the crash near Addis Ababa, Ethiopia AP Plane crash kills 157 in Ethiopia An Ethiopian Airlines Boeing 737 Max 8 (ET-AVM), the same type of aircraft that crashed EPA Plane crash kills 157 in Ethiopia Rescuers work at the scene of the crash near Addis Ababa, Ethiopia AP Plane crash kills 157 in Ethiopia Members of the search and rescue team work at the scene of the crash near Addis Ababa, Ethiopia Reuters Plane crash kills 157 in Ethiopia A boarding pass at the scene of the crash Reuters Plane crash kills 157 in Ethiopia Rescuers remove body bags from the scene of the crash near Addis Ababa AP Plane crash kills 157 in Ethiopia Wreckage at the scene of the Ethiopia Airlines flight AP

"Our customer relations team is responding to these customers individually, emphasising our friendly, no-change fee policy," America's fourth biggest airline said in a statement.

There has been no immediate indication as to why the plane went down in clear weather six minutes after departing Addis Ababa for the Kenyan capital Nairobi.

It was the second disaster involving the new 737 Max 8 in less than five months, after a flight operated by Indonesian budget airline Lion Air crashed into the sea in October, killing 189 passengers and crew.

China’s civil aviation administration ordered all airlines to ground the model – the latest version of Boeing’s most popular passenger jet on Monday.

“Given that two accidents both involved newly delivered Boeing 737-8 planes and happened during take-off phase, they have some degree of similarity,” it said.

Indonesia also said it would temporarily ground the aircraft for inspection.

Cayman Airways, the flag carrier of the British Caribbean territory, and South Africa's Comair have also suspended use of the model. Other airlines said they were monitoring the situation.

Alan Diehl, a former National Transportation Safety Board investigator, said reports of unstable vertical speed in the Ethiopian jet's ascent were "clearly suggesting a potential controllability problem."

However, experts cautioned against drawing comparisons between the Ethiopian Airlines and Lion Air disasters until more information was known.

Other possible causes of the crash include engine problems, pilot error, weight load, sabotage or bird strikes, Mr Diehl said.

“I do hope though that people will wait for the first results of the investigation instead of jumping to conclusions based on the very little facts that we know so far,” said Harro Ranter, founder of the Aviation Safety Network, which compiles information about accidents worldwide.

Indonesian investigators have not yet determined the cause of October’s crash, although they are probing whether faulty readings from a sensor might have triggered an automatic nose-down command to the plane.

Ethiopian Airlines said the jet that crashed on Sunday had undergone a “rigorous first check maintenance” on 4 February and no problems had been detected ahead of the disaster, according to the company's chief executive.

Pilot Yared Getachew had a "commendable record" and more than 8,000 hours of flying experience, according to the airline.

The plane’s black box flight recorder was recovered at the crash site on Monday, but officials said it was partially damaged and “we will see what we can retrieve from it”.

The aircraft was one of five 737 Max 8 planes the airline had received so far after ordering a fleet of 30. The remaining four in operation have been grounded until further further notice as an “extra safety precaution”, said spokesman Asrat Begashaw.

A Boeing spokeswoman told The Independent: “Safety is our number one priority and we are taking every measure to fully understand all aspects of this accident, working closely with the investigating team and all regulatory authorities involved.

“The investigation is in its early stages, but at this point, based on the information available, we do not have any basis to issue new guidance to operators.”

Ethiopian Airlines crash

Boeing has taken more than 4,700 orders of the model since it was launched in 2017.

A spokesman for Tui Airways, which became the first UK airline to receive a Boeing 737 Max 8 in December last year, said it had “no indication that we can’t operate our 737 Max in a safe way like we do with all other planes in our network”.

The company, which has 15 of the aircraft and plans to increase that number to 32, added it was “in close contact with the manufacturer”.

Scandinavian airline Norwegian, which serves London Gatwick, Manchester and Edinburgh in the UK, said the 18 Boeing 737 Max 8 aircraft in its fleet were “operating as normal” on Monday.

Cayman Airways, which operates two of the jets, said it had suspended them to maintain "undoubtable safe operations". Comair, which has one of the model in its fleet but

It came as details of the lives lost in Sunday's crash began to emerge. Victims spanned more than 35 nationalities, with most from Kenya, Canada, Ethiopia, China, Italy, the US, France, the UK, Egypt and Germany.

Nineteen employees of UN-affiliated organisations are thought to have been killed, with the disaster coming a day before an environmental forum was due to start in Nairobi on Monday.

They included Joanna Toole, 36, one of three Britons and one Irishman identified as having been on the plane.

A spokesperson for the UK's Foreign and Commonwealth Office said "at least nine British nationals" had been on board the flight.

"Our staff at the British Embassy in Addis Ababa are continuing to work with the relevant authorities in Ethiopia to obtain further information," the spokesperson added.

Joseph Waithaka, a dual Kenyan-British national, University of Plymouth graduate Sarah Auffret were also killed, and Irish aid worker Michael Ryan were also killed.