Clausotechnolometry explains Erotarandusdynamics

Yep, the technical term for the study of how reindeer fly.

Santa's answer:

Not all reindeer can fly, everyone knows that. So how do my reindeer fly? Well they are a rare breed indeed, but I have a team of elves that are dedicated to finding reindeer that are capable of what some call, the gas-bang theory.

This type of reindeer is so hard to find and that is why I've had the same reindeer for almost 179 years now. It also takes close to 350 years to train a reindeer, so you won't see any new ones for a long time because it takes a lot of work mastering gas-bang skills. So what are gas-bang skills?

Well the reindeer is capable of converting the gas generated from eating a lot of beans and cauliflower into a lighter gas than the oxygen found in the air. When this happens, it actually allows the reindeer to float, and the lighter the gas, the higher it can fly. And the reindeer that have been properly trained are able to control this gas properly so that it can safely fly at different altitudes.

As for steering, a combination of head movements and the unique shape of the hooves, allow the reindeer to guide my sleigh effectively.

And that's how my reindeer fly every Christmas Eve!