As a brand new "newbie" last year I was in my 3rd flight when my sister-in-law called causing me to lose the connection to the Phantom 3 Advanced Drone. I forgot to inactive my Apple iPhone 6s. So I decided to purchase a dedicated Chinese Android Phone (i.e no phone service) starting with the Leagoo M8 as it had a 5.7 inch screen. It worked OK with the Phantom 3 Advanced but not the Mavic Pro as I got video lag as it had only 1.3 GHz and had a quad core cpu. Sensing I needed a higher power CPU and more Ghz I purchased the Leagoo T10 ($134) and it worked great. Since then I've purchased a Le Eco S3 x626 ($95) and just recently a Xiaomi Mi Max 2 ($159). Each phone has either an octa core or deca core cpu and at least 2.0 Ghz. And they all work fine with my Mavic Pro Zoom, Mavic Pro, Mavic Air and Phantom 3 Advanced. I like the Xiaomi's larger screen but they all work fine. What is impressive is the battery power just never seems to go down as it did with the Apple that was used for everything. And there are no unnecessary apps on the phones to consume power - just those to operate the phone. I keep a phone in each drone carrying case so that I just grab and fly when the spirit moves me.