I'll say up front that I am new to RC and the Phantom 3 Professional. I followed every step in the book and watched several videos and was careful to observe safety rules. After several short test jumps to become familiar with the controls, we took the P3P to a large field and made three successful long flights. I changed the battery in the P3P and took it up again. It was up for just under 200 feet and out about 400 feet or so when the controller showed a green light and no white lights, and my android closed the DJI Pilot app. I was stuck there with no way to control the P3P. I tried numerous times to press the home button on the controller, and though I heard a beep, the phantom did not return. I tried to restart the app, but it would not start (android). Thanks to the excellent technology, when the battery got low on the P3P it came safely back. What would cause the DJI Pilot App to close and the controller to be unresponsive? How long does the controller battery normally run? Is there any way to bring a backup battery for the controller while out in the field? It is rather disturbing that I have four batteries for the P3P, but the controller may not be able to stay alive long enough to use the potential flight time.