WASHINGTON - US regulators on Monday ordered Boeing to make urgent improvements to the best-selling jet involved in a deadly Ethiopia plane crash -- but ruled out grounding the fleet as investigators worked to piece together the aircraft's final moments.
The Ethiopian Airlines Boeing 737 MAX 8 crashed minutes into a flight to Nairobi on Sunday, killing all 157 people on board and prompting airlines across the world to begin withdrawing the model from schedules.
The US Federal Aviation Administration (FAA) said it was working with local authorities and the National Transportation Safety Board and may soon share safety information concerning the aircraft.
"If we identify an issue that affects safety, the FAA will take immediate and appropriate action," it said in a statement.
The FAA said it was ordering Boeing to make improvements to anti-stalling software and the maneuvering system, giving the company until the end of April to make the updates.
Investigators have recovered the black box flight recorders from the airliner, which went down near Addis Ababa, just six minutes after takeoff, as the pilot alerted controllers of "difficulties."
There were passengers and crew from 35 countries on board, including some two dozen UN staff. Ethiopia decreed Monday a day of national mourning.
The aircraft was the same type of jet as the Indonesian Lion Air plane that crashed in October, killing 189 passengers and crew.
Not since the 1970s - when the McDonnell Douglas DC-10 had successive fatal incidents - has a new model been involved in two deadly accidents in such a short period.
The FAA acknowledged that the crashes were being linked in media reports but said the investigation had "just begun" and so far no data had been provided to "draw any conclusions or take any actions."
Airlines in Brazil, China, Ethiopia, Indonesia, South Africa, Mexico and other countries said they were suspending operations of their 737 MAX 8 fleets. Pilots from Argentina's Aerolinas Argentinas have refused to fly the aircraft.
The move caused Boeing shares to tumble around 12 percent earlier in the day, before recovering about half its losses by the close of the trading day.
The company said it was sending a technical team to the crash site and will work with Ethiopian and US regulators to determine the cause.
"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," Boeing said.
The plane that crashed on Sunday was less than four months old. Ethiopian Airlines said it was delivered on November 15. The airline grounded its fleet of six remaining Boeing 737 MAX 8 planes.
China also ordered domestic airlines to suspend commercial operation of the MAX 8.
There were eight Chinese nationals among the 149 passengers and eight crew on the Ethiopia flight.
Indonesia, which has 11 of the MAX 8 model planes, said it would carry out inspections and temporarily prohibit them from flying.
Some airlines said they were not canceling MAX 8 flights, including Oman Air, flydubai, Turkish Airlines and Russia's S7.
US airlines also appeared to remain confident in the manufacturer, and Canadian officials said they will not ground the three aircraft in use by domestic carriers.
Boeing has described the MAX series as its fastest-selling airplane ever, with more than 5,000 orders placed to date from about 100 customers.
State-owned Ethiopian Airlines, Africa's largest carrier, had ordered 30 MAX 8 jets in total, and China has received 76 from an order of 180.
The jet went down near the village of Tulu Fara, some 40 miles (60 kilometers) east of Addis Ababa.
Inhabitants of the remote area looked on from behind a security cordon as inspectors searched the crash site and excavated it with a mechanical digger.
The single-aisle Boeing jet left a deep, black crater at the impact site.
Ethiopian Airlines said the pilot was given clearance to turn around after indicating problems shortly before the plane disappeared from radar.
The airline's chief executive Tewolde GebreMariam said the plane had flown in from Johannesburg early Sunday, spent three hours in Addis and was "dispatched with no remark," meaning no problems were flagged, before leaving for Nairobi.
Author, student, aid workers
The crash cast a pall over a gathering of the UN Environment Programme as it opened in Nairobi. At least 22 staff from several UN agencies were onboard the doomed flight.
Delegates hugged and comforted one another as they arrived at the meeting with the UN flag flying at half-mast.
Passengers included tourists, business travelers and humanitarian workers.
Kenya had the highest death toll among the nationalities on the flight with 32, according to Ethiopian Airlines.
Canada was next with 18 victims.
There were nine Ethiopians and eight each from Italy and the United States. The airline said Britain and France each had seven people on board, Egypt six and Germany five.
France, however, put its death toll at nine.
Britain also put its death toll at nine, including two dual nationals traveling on other passports.
Italian archaeologist Sebastiano Tusa, 66, died in the crash, his wife Valeria Patrizia Li Vigni was quoted as saying by the Corriere della Sera newspaper.
On Sunday, "the friends I met at mass said I shouldn't worry because bad news travels fast," she said.
"In the end it arrived anyway, and it destroyed my life. I felt the disaster coming... He hadn't even wanted to go."