LeBron James -- Team Jet Turn Up ... After KO'ing Chicago

**Gentlemen, this is your captain speaking ... we've now reached 10,000 feet ... you're now free to PARTY YOUR FACES OFF!!!!**

LeBron James and the Cleveland Cavaliers wasted no time throwing a dance party on the team's private jet Thursday night ... celebrating their blowout win over the Bulls and moving on to the Eastern Conference Finals.

J.R. Smith shot footage of Bron gettin' down to The Dream's "That's My S**t" ... while teammates slugged beers and basked in the win.