We flew to BA using Viking air from Miami. Modified the reservation to go non stop. Our return to BA was on our own as we went to Torres del Paine National Park. Viking provided the flexibility we needed for flights and dates.
A note on Vikings on board service. Our trip occurred just after the rouge wave hit the ship. The workers started at 6AM and went right past our stateroom slamming a crew entry door. I went to guest services and asked if they could help. By the afternoon the issue was solved and everyone on Vikings staff new about it. It's easy when all goes well but Vikings staff was amazing.
Good luck on your planning