What would you do if your ex-boyfriend were on the same flight as you and your new girlfriend?! WWKSD? What would Kristen Stewart do? Well, she just rode it out ...

KStew and her first love RPatz shared a flight from France, returning to LA after Paris Fashion Week and both were in first class along with Kristen's model girlfriend Stella. We're told a few passengers in the cabin were freaking out, whispering amongst themselves and that the former lovers simply nodded at each other to acknowledge one another and then ceased all interaction for the rest of the flight.

When they touched down at LAX, Kristen and Stella went first and Rob's bodyguard held him back so as not to arrive at the paparazzi waiting outside at the same time -- lest they look like they were all three together!