I am about to become a U.S citizen (I am from korea, south obviously) though, I currently have a permanent residency visa here, I've traveled only by land to canada and mexico using it, however I read that traveling by air you will have to have a U.S passportso my question is, is it possible to travel with just a PR card to foreign countries by air? I have previously used my south korean passport but it recently expired and I don't think I'll be renewing it, thanks
nope. you'll need a passport.
they won't let you on the plane without a passport.