During the en route phase of an IFR flight, the pilot is advised 'Radar service terminated.' What action is appropriate?

When a pilot is advised that "Radar service terminated," it indicates that air traffic control (ATC) will no longer provide radar services for separation and monitoring. During this phase of an IFR flight, the pilot should resume normal position reporting procedures. This means the pilot will need to communicate their position at reporting points along their route to ensure situational awareness and maintain safe separation from other aircraft.

Setting the transponder to code 1200 is not appropriate in this scenario, as doing so would indicate the pilot is switching to VFR (Visual Flight Rules) operations, which is not the case during an IFR flight that is still in progress. Likewise, activating the IDENT feature of the transponder would only signal to ATC that you wish to draw attention to your aircraft on their radar, which does not substitute for the necessary position reports that the pilot must now provide due to the terminated radar service. Therefore, the appropriate action is to resume normal position reporting to comply with IFR regulations and maintain safe operations in the airspace.