Pulp Fiction-female Cab Driver Jumps Out The Window

What is the significance of the final scene of Birdman?

I must write SPOILER ALERT first but the question itself would mean there will be spoilers.Here is another explanation which i felt might be a valid one.There is a scene in which something is shown falling from the sky and then a few jellyfish are shown lying on the ocean which Riggan claims to have been bitten by.It is entirely possible that he was not human and he could actually do all the "telekinesis" and "flying" things.The scene were the cab driver shouts about not receiving money while exiting a building in which Riggan had entered flying.I think it was NOT shown that it was Riggan that had in fact not given the cab fare. So in fact Riggan might have actually flown in air as shown and the cab driver was shouting about some random guy who had also entered the building. Also, whenever Riggan uses his telekinesis or flying nobody was around till the last scene wher his daughter notices him flying off. So here is my theory, There are actually two different story lines beautifully entangled in the movie and it is left for us and our imagination to follow whichever one we want, one in which he is hallucinating and the other in which he actually can do all the supernatural stuff.P.S: only watched the movie once so my interpretation could be entirely wrong. But as of now I stand by my theory.In my theory he is satisfied with what he had attained with the end performance and chose to leave off to the place from where he had come from.