I am in the process of switching carriers.  I'll be getting a new phone when I do.  My old phone is a Smamsung Galaxy S7.  It works reasonably well with the Mavic controller and the DJI GO4 app (only crashed the app a few times).  I have a few questions:1.   I was wondering if I'll be able to use the old phone to fly with even though it won't be attached to a carrier or newtwork.  Can I use it just as a view screen and to record?  
2.  Will I be losing any functionality by having a phone not connected to a network?  

3.  I'm switching from Verizon to Metro PCS.  It appears that I cant take the Galaxy S 7 so I'm looking at choices for cheap phone.  I'm thinking the ZTE ZMAX Pro.  Has anyone had any experience with this phone?
Thanks in advance for any help you can give me.

I use a deactivated iPhone with my MP and it works great. What you lose is the maps functionality.  You have to either cache the maps of where you will be flying while you have access to wifi or hotspot to your new phone and use its cell data to update the map.

Many pilots turn on Airplane mode, so no network activities. You should be good but you may need make maps offline.

laceyboy Posted at 2017-5-17 09:27
Many pilots turn on Airplane mode, so no network activities. You should be good but you may need make maps offline.

laceyboy, Yes your right the maps have to be saved in the phone's cache to be used in airplane mode

Not saving maps wont stop you from flying.
I have a UMi EMax secondary phone with no network ability(no sim) AND airplane mode turned on to stop wifi/network searches which seem to interfere with reception.
I have never cached a map in my life and use my home network/wifi to upload stats when i get home, or view flight details with maps from home wifi.
To fly using your maps which might not be all that legal, just pre-install them if you can be bothered.

I am using a ZTE phone with no sim card and it works fine app has never crashed.

Hi Lobstah.
im pretty much doing that same thing. i had a metro pcs lg. i broke . it started working again. i got a cheap 39 $ s5  as i just need it to text and talk. i didnt add any apps to new phone that werent factory installed already except go 4. i flown bunch of times in airplane mode with wifi and location on . no probs as of yet. i also tried non activated phone. it also worked. like everyone else said, just make sure you are in wifi or download your maps.  I would also recommend , on the non activated phone you are going to use just for dji , restore phone to remove all non factory apps to original , then download the go 4 and no other apps if possible. this will help elliminate pop up and disconnects. hope this helps. good luck and happy flying!!

I use a deactivated (no cell service) S5 for my Mavic Pro flying and it is fine.