Invisible UFO snapped over Mesa, Arizona

On January 21, 2015, a UFO not visible to naked eye has been photographed several times over city of Mesa (in Maricopa County, Arizona). Photos indicate that this luminous moved slowly in the sky.

Witness statement:

These are actually my friend pics taken on her cellphone which actually takes impressive pics.

She likes to take random pics of the Arizona sky/clouds usually whenever she is out driving and thinks the sky looks pretty.

She was driving at the time pics were taken and she did not notice the object. It wasn't until the next day when she went to show me her latest sky pics that we noticed this object and that it was in a few of her pics taken in sequence and obviously it moves during the pics.
Thought we would send them in to you guys for review

thanks :)