It's a federal offence to swear on the radio. Not that it doesn't happen, but it's extremely rare. We all censor ourselves on the radio, because the style of speaking is different, so the same expressions don't slip out as easily. If you do hear cursing on the frequency, most of the time it's because someone doesn't realize their microphone is turned on. A flight service specialist with an open mic said some truly obscene things about me once and I probably could have got him in no end of trouble, but I didn't. Today a controller made me smile by leaving a space where the taboo word fit, but leaving me to fill in the blank.
We'd called for a clearance, and the controller vectored us one way and then the other, and couldn't give us a good altitude and then finally got us going. "Sorry for the ... show," he said, the missing word before show clearly distinguishable without being pronounced. There are some expressions in English that lack a good non-profane equivalent.