Yeah, it takes a while to form too many opinions. And you pretty much summarized what happened early. There were 3 flights leaving through 3 different routes. The one that was supposed to arrive first ended up arriving second, but it wasn't too far behind the first one.
The two girls and the older couple both switched from motorcycles to the helecopters. They actually lost quite a bit of time switching, but the girls were early enough to arrive at the detour in the first place, so if they had gone straight to the helecopters, there is a good chance they would have ended up a lot better off than they did.
The thing is, even though they older couple kept missing the clue box, they were at the bridge pretty early, too, so only a couple people passed them up (including the girls).
In the end, there were three couples that hit the helecopters at roughly the same time. For whatever reason, there were a lot of couples that went to the second closest destination building and the lifelong friends were just a bit behind. There is a good chance that there were still tickets available for the closest location still, but at that point, everyone was just trying to get up in the air. It's possible that taking an extra minute to find the closer location would have changed the end result.
As far as the two sisters being in last place the whole way, the lifelong friends were never that far ahead of them.
The only team that seemed to stand out to me was the hippie guys. They got on the first plane, which got delayed, so they were in the second group, then they managed to get back in front of most of the people that were on the first plane to arrive. Everyone else just sort of fell in order.