Sara Chalachew, Getnet Alemayehu, Sintayehu Aymeku, Mulusew Alemu has been working with Catholic Relief Services.
In a statement online, the charity said: "Although we are in mourning, we celebrate the lives of these colleagues and the selfless contributions they made to our mission, despite the risks and sacrifices that humanitarian work can often entail.
"Our thoughts and prayers are with their families and all of those who lost loved ones as a result of this tragedy."
157 people including nine Britons died in the crash.
On Wednesday, the Civil Aviation Authority (CAA) banned the Boeing's 737 Max plane from operating in the UK amid safety concerns.
A CAA spokesman said: "The UK Civil Aviation Authority has been closely monitoring the situation, however, as we do not currently have sufficient information from the flight data recorder, we have as a precautionary measure issued instructions to stop any commercial passenger flights from any operator arriving, departing or overflying UK airspace."
A number of countries and airlines around the world have also grounded 737 Max 8 aircraft, which was the model involved when Ethiopian Airlines flight ET302 crashed shortly after taking off from Addis Ababa on Sunday morning.
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