VN1672 was a routine flight from Vietnam Airlines between Da Nang and Haiphong, operated by the airline’s A321 of VN-A614, a seven-year-old airframe.
As you can see from the data above, the aircraft began to squawk the Hijack code at around 4,200 feet on its base leg into Haiphong.
At this stage, it is unclear whether this was indeed a hijacking event or whether it turned out to be a general emergency or a fault with ADS-B coverage.
Regardless, AviationSource has approached Vietnam Airlines for comment on this in the hopes that further clarification can be made over the incident.
This is a developing story.