Apple Watch - Airplane Mode
Airplane mode on Apple Watch, by default, mirrors the setting on your iPhone. When you disable Airplane mode on  your iPhone, it can not be mirrored to Apple Watch, because the radios on the watch are turned off. You need to disable Airplane mode on Apple Watch manually by using the interface on the Apple Watch.

You can disable the automatic mirroring of Airplane mode the following ways:

iPhone


Go to the "Apple Watch" app
"My Watch"
"General"
"Airplane Mode"
Make sure the "Mirror iPhone" switch is turned off.


Apple Watch - 


Go to the "Settings" app 
"Airplane Mode".
Make sure the "Airplane Mode" switch is turned off.