It’s not unusual for landing lights to illuminate the underside of an aircraft. So I would say this is an airplane with landing lights on.
This mysterious object is a 737. (My own photo.)
However in the OP photo:
-The reflected landing lights are illuminating the wings from wingtip to wingtip
-The reflected strobe is also illuminating the wings from wingtip to wingtip
So most likely this is a small plane or perhaps a helicopter. So far my best guess is that this a small – low wing- plane on approach to Flagstaff Pullman Airport to the south. Or a helicopter.
Another reason to think it’s a small aircraft. As you can see in my photo of a 737 heading away from the camera ... Read even more