A plane departing from Ho Chi Minh City for the north-central town of Vinh had to reroute to Hanoi on Tuesday due to technical problems, a Vietnam Airlines spokesman said, but alleged wrong warning signal sent by the captain triggered fears of hijacking.
Le Truong Giang, the airline spokesman, dismissed information that the flight had been hijacked.
Earlier, media reports including Vietnam News Agency quoted an unidentified source as saying that someone had tried to force his/her way into the cockpit, forcing the plane to reroute to Hanoi.
Vietnam Airlines reiterated in a statement late Tuesday that that the emergency landing had nothing to do with hijacking.
It said due to technical problems that led to reduced pressure, the pilots had to make the emergency landing at Hanoi's Noi Bai airport.
But Tuoi Tre (Youth) newspaper quoted another source as saying that when the plane descended from the height of 35,000 feet to 13,00 feet, its Czech captain, Pechanec Marek, falsely pressed the hijacking code (7500) instead of the emergency code (7700), inadvertently placing the flight under the state of hijacking vigilance.
The alleged wrong warning signal consequently send the ground contingency forces scrambling to brace for a hijacking scenario, according to the source.
Officials from the Ministry of Transport and the Civil Aviation Administration of Vietnam rushed to the airport to instruct investigative work.
A file photo shows a Vietnam Airlines airplane being refueled at Noi Bai Airport.
Pham Quy Tieu, deputy transport minister, called a meeting at the airport at 9:30 pm to review the case. Tieu said authorities concerned would open the flight recorder Wednesday to verify information that the flight captain had sent the wrong emergency signal.
The Airbus A321 plane, with 135 passengers and seven crew members on board, landed safely at Noi Bai at 7:15 pm, the Vietnam Airlines statement said. It said the planed has been commissioned by Vietnam Airlines since 2008.
"Further investigations [into the cause of the incident] will be underway," the statement said.
Of 135 passengers, 26 stayed at Noi Bai while the others were transferred to another Vinh-bound plane that took off at 9:40 pm.
News website VnExpress ran a photo purportedly taken from Facebook pages of several passengers of the flight. They were wearing oxygen masks, the photo showed.
VnExpress quoted airport authorities as saying that the pilots have been questioned to account for the emergency landing of the plane.
Currently, Vietnam Airlines operates three flights from HCMC to Vinh, the capital city of Nghe An Province, on a daily basis. The flight in trouble was the last of the day, taking off at 5:10 pm and scheduled to land in Vinh at 6:55 pm.