Testing iOS-app on device while offline

I have a paid Apple developer account. I'm using Xcode 8.0 with iOS 10.0.1 on an iPhone 6 plus.

Starting the app on the device works, I verified the developer app certificate on the iPhone.

So I want to test my app while device is offline on starting the app. In Xcode I got the message:

"Verify the Developer App certificate for your account is trusted on your device. Open Settings on iPhone Plus and navigate to General -> Device Management, then select your Developer App certificate to trust it."

I have to go online to verify. Then I go offline again and same thing happens.

My question: How to test an app on device while offline on starting the app?