Wouldn't keeping people on the plane until 6:30 cause a dangerous situation when everyone is eventually let off the plane? I know that if I was held on a plane, and I knew that everyone else on other planes was likely being held onboard, then as soon as I got off the plane, I'd go barreling down the hallway toward immigration like a baserunner trying to beat the ball to home plate, due to fear of being stuck in line.