OK, so they are all there at the cafe. That's cool, a happy ending, anyway. I just didn't catch the part about him escaping with the plane-thing on autopilot.
I think I heard a gasp from someone in the theater when Alfred returned to the cafe, before Bruce and Selina were even spotted, apparently because the person making that noise could see where things were going just by Alfred showing up there. But that gasp could've happened in the previous scene where it was revealed that the autopilot had actually been operational. At that point we pretty much knew that David Letterman had been joking.