I have some ideas for how Nintendo can alleviate the online issues of players joining (excuse me if these have already been suggested):
1: Make the inside of the airport a holding lobby and allow the joining players to collect in there. Then the host gets to decide when they can all move to the island together.
2. Airport lobby is again a holding area, but there is a countdown and whichever players are there exit the airport at the same time. No more can come to the Island.
3. The host sets a limit of joining players and they are automatically released when the threshold is achieved and the gate is closed to any additional travelers. Otherwise, like above, the host can allow guests on the island when they see fit or there is a countdown.
4. You have players book their trip with a time of departure/arrival. The game does a 5 minute countdown to when you have to board the plane. Everyone arrives at the same time.
These are never going to happen and maybe make no technical sense, but I feel there is a solution to the constant loading screens for those folks playing online with big groups.