Flight 302, a Boeing 737, was believed to be carrying 149 passengers and eight crew members on its way to Nairobi, the Kenyan capital.
It took off from Bole International Airport in Addis Ababa, the Ethiopian capital, at 8:38 a.m. local time and lost contact six minutes later, the airline said.
The plane is believed to have gone down near Bishoftu, southeast of Addis Ababa, the airline said in a statement.
The airline said it had not confirmed any casualties or whether there were any survivors.
The prime minister’s office expressed its condolences on Twitter.