A few of us private messaged him to find out if our guess was right and may have added to the confusion.
Anyway, isn't we already know Santa can operate outside of the laws of physics since he can either bend time/space, has mastered the answers to string theory, and can shift into an elongated form to get into locked houses through chimneys or key holes in doors.
So I think the reindeer fly on magic dust or something right? I think he tore off one of the reindeer's heads, shook out some of the flying dust on the presents and then the presents would obviously float and he could just move them over the bridge. Thus presenting us with a reasonable answer using previous facts such as flying reindeer.
Otherwise he could shapeshift.. ooh.. transform into a glider and fly over the canyon.