When sperm hits the air does it die?

NO. This may be a misconception for couples using the "pull out method" for contraception. Sperm may not be viable for long "out in the air" however, if you are using the pull out method for contraception, normal sperm are very active and strong swimmers, so even if most of ejaculation happens after "pull out" and , even small amounts left close to the vagina, can make a bee line to the womb.