Funny enough, due to a tailwind the other day, flights a couple days ago across the Atlantic actually did break the sound barrier. Look at this IAD>LHR flight that reached 802 mph [0]. (It was a Boeing).
Nah; its groundspeed might have been more than the speed of sound, but "breaking the sound barrier" refers to your speed through an airmass (i.e. airspeed). It doesn't count if you're just getting a big tailwind.