Do you need to have cell service to be able to see the video on your phone while flying? Sometimes when I have no service and try to connect my phone it does not show any video and I have to fly the drone blind (resulting in bad footage).

You do NOT need cell service to view the live AC video while flying.  If you a "Dropping" video while flying, I STRONGLY suggest you look into why that's happening.  If not, you will be joining "I lost my Mavic while flying over water" club.

What device are you using?

No, you don't have to use the cell service or cellular to connect the RC and mobile device. In your case, I suggest that you can try to switch the phone to airplane mode first and test if it is the same result. If yes, I suggest that you can try to change another place, or reinstall the latest app and see if it helps, please note to do a backup like syncing the flight record and saving the pictures and videos before your reinstallation.
If the issue persists, please provide me with the screenshot of the app, the app version and the mobile device you are using, I would like to check more. Thanks.

Woe Posted at 2018-1-16 15:28
What device are you using?

i have only tried using the iPhone 6 both mine and someone elses