"Ethiopian Airlines is one of the safest airlines in the world. At this stage we can not rule out anything", CEO Tewolde Gebremariam told reporters.
"At this time search and rescue operations are in progress and we have no confirmed information about survivors or any possible causalities".
Around the world, families were gripped by grief.
Data released by the Sweden-based service suggested the aircraft had climbed nearly 1,000 feet after taking off from Addis Ababa, a hot and high-altitude airport whose thinner air requires extra effort from an aircraft's engines.
The Addis Ababa-Nairobi route links East Africa's two largest economic powers and is popular with tourists making their way to safaris and other destinations.
Canada, Ethiopia, the U.S., China, Italy, France, Britain, Egypt, Germany, India and Slovakia all lost four or more citizens.
"We extend our heartfelt sympathies to the families and loved ones of the passengers and crew on board and stand ready to support the Ethiopian Airlines team", it said.
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Smollett was initially charged with one count of lying to the authorities on February 20. They became cooperating witnesses and were released without charges.
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The trust had received many sightings of female travellers matching Ms Shaw's description and had to work through several leads. A puppy which Ms Shaw took with her when she left the accommodation was found at the peak of the hiking trail on Friday morning.
Ethiopian officials declared Monday a national day of mourning.
Agnes Muilu said he came to pick up his brother. A preliminary report issued in November, before the cockpit voice recorder was recovered, focused on airline maintenance and training and the response of a Boeing anti-stall system to a recently replaced sensor, but did not give a reason for the crash.
It's unusual for authorities to take the step of grounding planes, and it's up to each country to set standards on which planes can fly and how those planes are maintained, said Todd Curtis, an aviation safety analyst who directs the Airsafe.com Foundation.
Safety experts cautioned against drawing too many comparisons between the two crashes until more is known about Sunday's disaster.
Ethiopian Airlines confirmed online that the aircraft registration was ET-AVJ, a four-month-old aircraft, which was delivered in November of past year. ET-AVJ had over 1,000 hours with the airline since delivery.
The aircraft departed Bole International Airport at 8:38 a.m. and contact was lost at approximately 8:44 a.m. local time, according to the airline.
"Data from Flightradar24 ADS-B network show that vertical speed was unstable after take off", the Swedish-based flight tracking organization said on its Twitter feed. Analysts, however, predicted that Ethiopian Airlines would be the exception on the continent. Boeing planned to send a technical team to Ethiopia.
The Boeing 737 reportedly went down minutes after taking off Addis Ababa airport in Ethiopia's capital on Sunday morning. The flight has crashed 60km south-east of the airport.