Question: How does the Home Operator revoke a user's subscription authorization for operating Aerial UEs?
Option 1: By sending a revocation message directly to the UE.
Option 2: By updating the user's subscription information in HSS, which is then transferred to the MME via Update Location message during Attach and Tracking Area Update procedures.
Option 3: By sending a revocation request to the eNodeB, which then notifies the MME to update the user's subscription information.
Option 4: By contacting the MME directly to revoke the user's subscription authorization.
Explanation: According to the text, Home Operator may revoke user's subscription authorisation for operating Aerial UEs at any time by updating the user's subscription information in HSS. This updated information is then transferred to the MME via Update Location message during Attach and Tracking Area Update procedures.