I don't think it'll be horrid because you aren't doing any actions on that flight, just letting it take you for a ride.

I have noticed though, that unless you're running a 1GB + card that those things will slow you down quite a bit because all of those textures need to load. (Of course this depends on your draw distance and what effects you have turned on, along with how many clients you run).

People still play single characters with cards that are 5 years old and Blizzard wants the game and zones to be accessible for them.