Once you select the Fly option from the mission planning screen, Site Scan will go through a series of checks to make sure that the aircraft is ready to take off.
Once these checks are finished, Site Scan will prompt you once again to check your takeoff point and give the aircraft permission to start the mission.
Now that the aircraft is flying, you will have telemetry along the top of the screen. From left to right, the telemetry is as follows: Distance from the home point, altitude, charge of batteries, and satellites in range. You can switch between a variety of views while the mission is in progress.