Instrument Flight Rules (IFR) En-Route Navigation
Flight plan is always required for IFR flights, your instruments or the autopilot navigation system can be used to navigate and follow your flight plan. Make sure to modify your cruising altitude to satisfy terrain clearance and IFR Semi-Circular rules. If you are approaching controlled airspace, make sure to tune in and listen out for other traffic.
Source: Instrument Flight Rules (IFR) En-Route Navigation | Infinite Flight