An oldie, but a goodieSpy explains the effects of atmospheric re-entry: "Three hundred and fifty-three thousand tons of reindeer and presents are going to create an enormous amount of air resistance especially at 650 miles per second. This air resistance will heat the reindeer in the same way that spaceships are heated up when they re nter the earth s atmosphere. According to our calculations, the lead pair of reindeer will absorb 14.3 quintillion joules of energy per second each. This means they will burst into spectacular, multicoloured flames almost instantaneously, exposing the reindeer behind them. As Santa continues on his mission leaving deafening sonic booms in his wake charred reindeer will constantly be sloughed off. All 214,200 reindeer will be dead within 4.36 thousandths of a second."
Ten years ago in Spy [fawny.org]