"The flight was not hijacked as reported earlier," Vietnam Airlines spokesman Le Truong Giang told dpa.
After departing from Ho Chi Minh City Tuesday for Vinh, low cabin pressure forced the Vietnam Airlines plane to reduce altitude from11,000 metres to 4,000 metres, Vietnam Airlines said in a statement.
The crew then requested an emergency landing at Noi Bai airport, outside Hanoi. When alerting ground staff the pilot typed in the code for "unlawful interference," 7500, instead of 7700, which is for a general emergency, triggering preparations for a hijack, newspaper Tuoi Tre said. The emergency landing was necessary "due to a technical error," not a takeover of the plane, the company spokesman said.