How do you activate your VFR flight plan?

Activating a VFR flight plan involves communicating with air traffic control or a flight service station while you are airborne. This is typically done through radio communication once you are in flight. When you are ready to activate your flight plan, you can contact the appropriate facility and provide them with your flight plan details, such as your aircraft's location, intended route, and destination. This method ensures that your flight plan is active and allows for tracking and safety measures in the event of an emergency.

The other options do not accurately describe the procedure for activating a VFR flight plan. Sending a text message is not a recognized method for this process, and while you may file a flight plan at the departure airport, that by itself does not mean the plan is active. Additionally, the pre-flight inspection is focused on checking the aircraft's readiness and safety, rather than on activating the flight plan itself.