When do Class D airspace rules apply as Class G airspace?

Class D airspace is typically established around airports with an operational control tower, and it has specific entry requirements and operational rules to ensure safety in the vicinity of that airport. When the control tower is not operational, Class D airspace is considered to revert to Class G airspace rules. This means that the more relaxed regulations of Class G airspace apply, allowing for less structured flying, particularly regarding communication and visibility requirements.

Class G airspace is uncontrolled airspace, which lacks the stringent communication and clearance requirements necessary in Class D airspace when the tower is operational. This reversion to Class G conditions allows pilots to operate with greater flexibility under certain circumstances, although pilots must still exercise caution and awareness of other air traffic and weather conditions during their flights.

In contrast, the other options provided do not accurately describe scenarios in which Class D airspace behaves like Class G. Bad weather, nighttime operations, and flying above 5,000 feet do not necessarily correlate with the operational status of a control tower and do not affect the classification of airspace in the same way that the operational status of a control tower does. Thus, only outside control tower operational hours correctly describes when Class D airspace rules apply as Class G airspace.