The 2020 collapse and sale of Virgin Australia is still having aftershocks as the airline's new owners have dropped their long-term connection to Delta Airlines and forged a new alliance with United Airlines.
The Delta connection was originally a very tight one; the two airlines had a joint venture that allowed them to coordinate fares and schedules. It allowed VA and Delta passengers arriving in each other's countries to continue on partner domestic routes. The joint venture was not renewed in 2020.
At the same time, VA had close ties with Singapore Airlines and Japan's ANA, both Star Alliance members while Delta is a key member of Sky Team. VA's new owners have eliminated international routes and concentrated on rebuilding the company as a strong domestic airline. VA has now joined Star Alliance, giving it an Australia connection for the first time in years.
For Delta passengers and frequent flyers, the change means that starting in June they will need to buy their Australia domestic tickets separately from Qantas or VA. There will be little effect for VA passengers headed to the U.S. since they will be routed for domestic legs on United instead of Delta.