KoopAir
KoopAir is the name of an airline run by some of Mario's enemies. It appeared twice in the German Club Nintendo comics, but it never appeared in any Super Mario games.
The airline made its first appearance in the 1993 comic "Super Mario: Erholung? Nein, danke!." Mario, together with Luigi, Princess Peach and Yoshi, travels to Koopabiza using a KoopAir plane (pictured). Not only it looks very brittle from the outside, the on-board service (with Wendy O. Koopa serving as the stewardess) is also poor. Still, somehow the four friends reach their destination safely. Later, in the 1995 comic "Mario's Picross," Mario booked a flight with KoopAir again, to go on vacation in Egypt. This time, the plane does not look damaged, but the steward Bowser pushes him out of the plane right above Egypt. In both stories, it is mentioned that Mario booked a cheap holiday, explaining the poor service of the airline.
