Check out The Sky at the Mayan Ruins of Tulum

My final word on this one. Just based on that one photograph, it is impossible to say for sure what it is, I say a bird, others will dispute that..but.

If you want it to be a craft of some kind, that's what you will see.

If you want to see a bird, that's what you will see.

We could discuss forever what it is, but it will never be proven one way or another. Just chalk this up as another questionable photo.