A jamming signal at Vietnam's biggest airport interrupted communications between air traffic control and incoming planes, forcing pilots to circle or divert, an official said.
Controllers at Tan Son Nhat airport in Ho Chi Minh City lost contact with planes at 7.47 am on Tuesday (10.47 AEST), Deputy Transport Minister Pham Quy Tieu said.
Contact was lost for 18 minutes, according to a press release by the Civil Aviation Administration of Vietnam (CAAV) late Tuesday.
Six inbound aircraft circled, another landed at a nearby airport, while departing flights were delayed, the press release said.
A very strong and unknown radio frequency disrupted the air control system, said Tieu, adding that equipment to create such jamming signals is small and easy to obtain.
Vietnam Air Traffic Management Corporation was working with the Authority of Radio Frequency Management to find the cause, the corporation's chairman Dinh Viet Thang said.
There was no threat to aviation security, and the incident was "less serious than the blackout last November," Tieu said.
More than 90 flights were delayed or rerouted when power was cut to the Tan Son Nhat control tower and its radar for 90 minutes in November.
A technician was charged with violating regulations over the incident at Vietnam's largest airport, which receives more than 20 million passengers a year.
