We are on the May 24 Viking Ullur Buch to Budapest with pre- and post- extensions. I thought that I would try to get seat assignments. It took me nearly two hours to get seat assignments on our Austrian Air flight from Palm Beach International to Newark to Vienna through Viking Air! We were booked to Bucharest on United, and the flight to Newark was easy to get seats on the United site, but it turns out that the Newark to Vienna to Bucharest are Austrian Air flights. First I tried to get seat assignments on both the Viking Air and United web sites without success. I called Viking Air, who told me that they couldn't make the seat assignment because the flight wasn't booked yet but suggested that I call Austrian Air (800-843-0002). Austrian told me that I would have to pay 100 euros for advanced seat assignments, which I found outrageous considering how much we spent for premium economy. But they said that the 2-4-2 cabin was almost full, and the only way to get the 2 seats was to buy it now. I reluctantly agreed, but when they tried to charge my credit card, it wouldn't go through, again because the flight wasn't booked yet. Next I called Viking again and was connected to Viking Air Plus. The agent said that I hadn't paid for Air Plus so she couldn't help me even to connect me to regular Viking Air unless I paid for Air Plus first! Then I called Viking back and asked for regular Viking Air. That agent was able to get me seat assignments on the Austrian Air flight with no trouble and no cost.
Then I tried to get seats for the return on American through Amsterdam and Philadelphia to PBI. I had no trouble doing that on the American web site. But then that flight disappeared, and we were coming home on Delta through Paris to Altanta to PBI. Luckily I'm a 2M miler on Delta, so they were happy to give me seats. Of course none of these reservations are actually booked yet, and everything could still change.
We have another cruise from Iceland to New York later in the year. After this experience, we decided to book the tickets ourselves with Iceland Air rather than go through all of this again with Viking. We were actually able to book business class on Iceland Air for less than Viking was going to charge us for what was supposed to be Premium Economy on Delta but turned out to be just economy plus (which are not much better than economy). The only reason I can see to use Viking Air is that they take good care of you if there are cancellations or delays and provide airport transportation. So we booked Iceland Air a day early. The hotel and airport transportation is a little costly, but we get an extra day in Reykjavik.