Which of the following conditions does NOT require flying under IFR?

Flying under Visual Flight Rules (VFR) is primarily dependent on weather conditions and the ability of the pilot to maintain visual reference to the ground and other aircraft. When the weather is suitable for VFR, pilots can operate without filing an IFR flight plan. This means that when conditions permit VFR flight, it would not be mandatory to operate under Instrument Flight Rules (IFR).

The other conditions listed require adherence to IFR guidelines. For example, operating at night typically has specific regulations which may necessitate flying under IFR for safety, especially in limited visibility. Similarly, flying in federal airways requires aircraft to operate under IFR. Additionally, flying at high speeds, such as above 180 knots True Airspeed (KTAS), might also involve IFR requirements due to airspace regulations and the need for air traffic control separation. Therefore, the reasoning behind the preference for VFR in suitable conditions establishes that weather-permitting VFR flight does not mandate IFR.