These aircraft are always owned by a specific airline and not the alliance itself. Just look closer, you'll see the airline's branding somewhere on the aircraft

These aircraft are always owned by a specific airline and not the alliance itself. Just look closer, you'll see the airline's branding somewhere on the aircraft. The alliance branding is just meant to promote the alliance. These aircraft are part of their respective airline's fleet and operated as normal flights by the airline that owns it (just like other normally branded aircrafts).