A Myanmar military plane carrying 104 people went missing on Wednesday over the Andaman Sea, sparking an air and sea search.
"Communication was lost suddenly at about 1:35 pm (07:05 GMT) when it reached about 20 miles west of Dawei town," the office of military commander-in-chief Min Aung Hlaing said in a statement.
Four naval ships and two air force planes have been sent to search for the plane, which was flying between the southern city of Myeik and Yangon at more than 18,000 feet when it went missing.
Dawei is a port town an hour's flight south of Yangon, Myanmar's commercial capital.
The office said 90 passengers -- servicemen from Myeik air force command and family members -- were on board as well as 14 crew members.
It said the plane was delivered in March last year and had 809 flying hours.
"We think it was a technical failure. Weather is fine there," an airport source told AFP, asking not to be named, adding there was no news of the plane so far.
Myanmar's military fleet has a chequered recent history of plane crashes.
All five crew died when an air force plane burst into flames soon after taking off from the capital Naypyidaw in February last year.
Three army officers were killed in June when their Mi-2 helicopter crashed into a hillside and burst into flames in south-central Bago.
The missing plane is a Y-8F-200 four-engine turboprop, a Chinese-made model still commonly used by Myanmar's military for transporting cargo.
The former military junta bought many of the aircraft from Myanmar's giant neighbour during their 50 years of isolated rule, when they were squeezed by Western sanctions.
A former executive at Myanmar's aviation ministry said it was one of China's most popular military and civilian transport aircraft.
A surge in demand for air travel as Myanmar opens up has stretched the impoverished country's aviation infrastructure, in particular in remote airports.
Commercial jets have also suffered frequent incidents.
The worst in recent years was in 2012 when an Air Bagan jet crash-landed in thick fog and burst into flames short of the runway at Heho airport, killing one passenger and a motorcyclist on the ground.