Class II navigation when the flight operates in an area  outside the operational service volumes of federal VORs.  Class II navigation does not automatically require the  use of long-range, specialized navigational systems if  special navigational techniques are used to supplement  conventional NAVAIDs. Class II navigation includes  transoceanic operations and operations in desolate and  remote land areas, such as the Arctic. The primary types  of specialized navigational systems approved for Class II  operations include inertial navigation system (INS), Doppler,  and global positioning system (GPS). Figure 3-1 provides  several examples of Class I and II navigation.  Planning the descent from cruise is important because of  the need to dissipate altitude and airspeed in order to arrive  at the approach gate properly configured. Descending early  results in more flight at low altitudes with increased fuel  consumption, and starting down late results in problems  controlling both airspeed and descent rates on the  approach. Prior to flight, pilots need to calculate the fuel,  time, and distance required to descend from the cruising  altitude to the approach gate altitude for the specific  instrument approach at the destination airport. While  in flight prior to the descent, it is important for pilots to  verify landing weather to include winds at their intended  destination. Inclimate weather at the destination airport can  cause slower descents and missed approaches that require  a sufficient amount of fuel that should be calculated prior to  starting the descent. In order to plan the descent, the pilot  needs to know the cruise altitude, approach gate altitude  or initial approach fix altitude, descent groundspeed, and  Descent Planning  C L A S S  I  C L A S S  I  C L A S S  I  C L A S S  I  C L A S S  I  C L A S S  I  VORTAC A  VORTAC B  Route 1  Route 2  CLASS II  1 hour or less  CLASS II  more than 1 hour  Route 3  The area encompassed by the cylinders represents the volume of airspace within the operational service volume  (OSV) of ICAO standard NAVAIDs. The altitude of your aircraft with respect to the location of the NAVAID is a  primary factor in determining OSV range.”  Your aircraft navigating from A to B is conducting Class I navigation because you remain within the OSV of  ICAO standard NAVAIDs during your entire flight.  Your aircraft navigating from A to B is conducting Class I navigation while within the OSV of the NAVAIDs.  You are conducting Class II navigation during the portion of your route outside the OSV of the NAVAIDs.  Because the duration of the Class II navigation is 1 hour or less, long-range navigation equipment or a flight  navigator may not be required.  Your aircraft navigating from A to B is conducting Class I navigation while within the OSV of the NAVAIDs.  You are conducting Class II navigation when outside the OSV of the NAVAIDs. The duration of the Class II  navigation is more than 1 hour. Therefore, long-range navigation equipment or a flight navigator is required.  NOTE:  Route 1  Route 2  Route 3  Figure 3-1. Example of Class I and II navigation.  3-3 