[This story has probably been around longer than I'm alive. I did do a little editing, but it's certainly not original. Wish I knew exactly who to credit.]
Pilots have to be certified by the Federal Aviation Administration, which initially involves a lot of school and practice and--finally--a ride with an examiner who distracts the potential pilot with a lot of questions while they're flying. The examiner also makes the pilot do things like induce a stall and then get out of it. Pretty much anything the examiner wants to test is fair game. He could, if he wanted, just reach over and turn off the engine. Once a pilot has his/her certificate, they get to be reexamined every so often.
Santa Claus, like all pilots, gets regular visits from the Federal Aviation Administration, and it was shortly before Christmas when the FAA examiner was scheduled to arrive. In preparation, Santa had the elves wash the sled and bathe all the reindeer. Santa got his logbook out and made sure all his paperwork was in order.
The examiner arrived. He walked around the sled slowly, paying attention to every detail. He carefully checked the reindeer harnesses, the landing gear, and Rudolf's nose. He painstakingly reviewed Santa's weight and balance calculations for sled's enormous payload.
Finally, they were ready for the checkride.
Santa got in and fastened his seatbelt and shoulder harness and checked the compass. Then the examiner hopped in carrying, to Santa's surprise, a shotgun. Santa's brow furrowed and he turned his head askew.
"What's that for?"
The examiner winked.
"I'm not supposed to tell you this, but you're gonna lose an engine on takeoff."