What should I do to use a mobile without a sim card?

Hi bud
I've been flying my MP with a Sony Z5 without a sim card with no problems at all, in fact I switch to airplane mode. Obviously you will need WiFi at home to up date your drone.
May I say I'm very new to all this flying lark but had some great help from this forum and the Internet in general.

Your phone doesn't need to have a slim card. Most here fly with IPads

Hi, thank you for the inquiry. We're hoping that you could get the best recommendation from our valued DJI Forum members in regards to using a mobile device without sim card. Please let us know if you have other concerns. Thank you for continued support.

Connect the mobile to your WiFi while still at home to download a map of where you intend to fly. Zoom in to cache the map to your mobile, it will then be available when you reach your chosen flying location

Even if you do have a sim card, it is necessary to download maps at home if there is no mobile coverage where you intend to fly - something I sometimes discover too late.  

Not entirely sure what the question is?