User blog comment:Miskos3/Fairy Tail 531: Pegasus vs. Black Dragon/@comment-173.54.225.116-20170417041154/@comment-7418318-20170417061221

Maybe contradictory, but certainly consistent since the very beginning of the series.

Whenever a sufficiently developed Dragon Slayer is on board any kind of vehicle, whether it floats, drives or swims, has an engine or is pulled by animals... they get sick.

It makes no sense, but as I said at least it's consistent.