Flashing Light over AZ

I was flying from LV to PHX sitting on the left side of the plane.
It was about 1:55am (rerouted flight.) The cloud cover was pretty thick so you couldn't see the ground, and there was no moon.

I was looking out the window and and saw a flash of light on the horizon
it was very bright white and lasted a second. Looking at a map here I am guessing that it was somewhere over the Haulapai indian reservation or Shivwits platue again it was a cloudy and not being able to see the lights of kingman or a highway I couldn't get any bearings.

After I saw it I Immediatly woke my wife up, she really didn't care too much. But I kept looking and saw it again only this time it wasn't as bright.
after that we were past whereever the light was flashing. I would guess that the time between the flashes is about 3 mins maybe 4.

Anyone ever see anything like this?

I think that i need to emphazise the size of this flashing light. it had to have been at least a mile wide. I can't think that i am the only one who saw this. If it has happened that night it probably has happened before.

I wanted to talk to the capt of the plane, to ask him if he saw it which he must of, but he was unavailble when I exited the plane.

Hmm.If it was a UFO,the pilots in the plane you're on board would have notice it too.Surely there would be some kind of flight response like flying away from those lights.Anyways,what you saw could be some sort of weather anomalies.Not everything that is weird you saw in the sky is some kind of UFO's doing.It could be just mother nature doing her thing.Well that's my input on your experience.