"This is the second major, fatal accident involving the Boeing 737 MAX 8 in less than five months, including October's Lion Air crash", Macheras told DW.
Caribbean airline Cayman Airways said it would also temporarily ground its two 737 Max 8 planes.
A statement by the airline earlier on Sunday said a search and rescue operation was underway.
Air traffic monitor Flightradar24 reported that the plane's "vertical speed was unstable after take-off".
Records show that the plane was new. The pilot was a senior aviator, joining the airline in 2010, the CEO said.
The Boeing 737 plane took off from Addis Ababa at 8:38 AM local time, and crashed shortly after at 8:44 AM. It was on a regularly scheduled flight from Addis Ababa to Nairobi, Kenya.
GebreMariam said they have not yet determined the cause of the crash.
Kenya's transport secretary James Macharia told reporters there were nationals from at least 35 different countries on board the Ethiopian Airlines flight 302, including the passengers from the UK.
The crash shattered more than two years of relative calm in Africa, where travel had always been chaotic.
Ethiopian Airlines said its CEO "expresses his profound sympathy and condolences to the families and loves ones of passengers and crew who lost their lives in this tragic accident". ET-AVJ had over 1,000 hours with the airline since delivery.
In the USA, the Federal Aviation Administration said it would join the National Transportation Safety Board in assisting Ethiopian authorities with the crash investigation.
New Prime Minister Abiy Ahmed has been promising to open up the state-owned airline to domestic and global investors.
A statement from the airline said it crashed around 31 miles south of the capital.
Speaking at the inauguration, the prime minister challenged the airline to build a new "Airport City" terminal in Bishoftu - where Sunday's crash occurred.