The Kardashian clan's jet touched down in Sin City early Saturday morning ... with Kim Kardashian, Khloe Kardashian and Kendall Jenner all bundled up and clambering out of their private jet.

They kept a fairly low profile ... Kim covering up with a hat while all three of the ladies used big sunglasses to cover parts of their faces as they made their way from the airport to their luxurious accommodations.

Big reveal at the hotel though ... because a man in a huge puffy coat, white beanie decorated with a black palm tree, and blue jeans on -- and with style choices like those this could only be Justin Bieber!!!

At least, we're pretty sure it's Biebs ... check out the pics for yourself. It definitely looks like JB from the back, and he's carrying what seems to be a Louis Vuitton dog carrier -- and we only really know one celeb who regularly schleps that around.

Of course ... Justin's tight with the Kardashian family -- particularly Kendall and Kylie Jenner through his wife Hailey, so flying with them isn't totally surprising.

And, we broke the story ... Usher's personally been in contact with his protégé about performing during the Super Bowl Halftime show -- not handlers passing messages between the two, but direct communication.

So, it looks like Justin took Usher up on his offer ... or he just wants to take in the game with his pals. Either way, we're definitely probably sure that's Justin!

Bottom line ... celebs not named Taylor Swift are trickling into Vegas before Sunday's 3:30 kickoff -- and there may be a few more surprises in store for fans.