Vietnam Airlines inaugurated direct flights between Vietnam and the United Kingdom in 2013.
Vietnam Airlines inaugurated direct flights between Hanoi and Ho Chi Minh City to London Gatwick on the 08 December 2013.
Vietnam Airlines transferred their London flights from London Gatwick to London Heathrow at the start of the IATA 2015 summer season on the 31 March 2015.
Vietnam Airlines is part of the Skyteam alliance and is the national flag carrier for Vietnam.
I'm sure that Heathrow Airport Limited would like Vietnam Airlines to remain at the United Kingdom's major hub airport.
Can HAL over rule ACL in situations like this?
The Vietnamese carrier Bamboo Airways were given temporary slots at LHR during the pandemic but have since relocated to LGW.
If indeed Vietnam Airlines do lose their LHR slots then it will surely be a loss to the airports airline portfolio meaning that the United Kingdom's major hub airport will no longer have direct flights to Vietnam.
I don't think that STN is really suitable for Vietnam Airlines, a return to LGW would have been a better option. If the airline does indeed relocate from LHR to STN I can't see it lasting for long. It will more than likely be a similar situation to when Garuda Indonesian relocated from LGW to LHR. For most airlines that would have been a successful move but it wasn't the case for GA.