text: Chapter 2
  2-56. Pilots fly in one of two altitude modes.
  MODE 1
  2-57. When the air defense threat keeps flight altitudes below those established by AR 95-1
  (for standard instrument flight), then pilots can fly at least 1,000 feet over mountainous terrain, and 500
  feet over flat terrain.
  MODE 2
  2-58. When the threat limits flight altitudes to the least possible clearances, pilots can fly as low as 50 to
  500 feet above the ground, regardless of terrain.
  AIR ROUTES
  2-59. Aircraft traffic management personnel (and pathfinders) can expect to move their equipment as
  often as every four hours, depending on the threat. Terrain, weather, and, most importantly, whether the
  enemy could intercept friendly aircraft from that location, determine when to move.
  THREAT AND TERRAIN
  2-60. In many instances, the threat and terrain prohibit a straight-line flight between the takeoff (liftoff)
  point and the destination (Figure 2-2). This applies to both Modes 1 and 2.
  FLIGHT MONITORING AND LANDING ZONE APPROACH
  2-61. Enemy presence keeps the pathfinders from using nondirectional beacons. However, for pilots to
  approach and land on the LZ visually, they need good visibility. Using radio homing signals for directional
  guidance presents a dubious option. Whether or not aircraft traffic-management personnel decide to use
  this electronic device, they should try to orient its signal away from the FEBA. This reduces the chance of
  detection.