text: FM 7-100.1________________________________________________________________________________
  requests and identifies the missions that can be supported by army aviation
  and those that must be supported with Air Force assets. The allocations are
  then sent to the theater commander for approval.
  8-25. At OSC level, the commander consults his CAO and develops detailed
  targeting plans for the current fight through the next 48 hours. He also
  makes rough estimates for 5 subsequent days. Requests are formulated for
  mission type, not for specific type of aircraft. For example, the OSC does not
  identify helicopters in its request for DAS. These requests are forwarded to
  the theater CAO and continually revised until 48 hours prior to execution.
  Once approved, these become part of the published theater aviation support
  plan (ASP). There can also be an ASP at OSC level, particularly when the
  OSC is not subordinate to a theater headquarters.
  8-26. Then, the theater or OSC AOS issues the ASP to the executing aviation
  units. These orders cover targets, numbers of sorties, air approach corridors,
  communications codes, and mission timing. Air Force representatives at sub-
  ordinate levels then confirm, for their respective commanders, the allocation
  of air resources. Normally, the commander holds a percentage of his air
  power in reserve to meet the unforeseen demands.
  8-27. Once the allocation is received by the OSC, the OSC commander may
  assign specific air support to a subordinate unit or maintain control at his
  level. The OSC AOS then continues to coordinate the effort until the end of
  the mission.
  MISSION REQUEST TYPES
  8-28. The OPFOR recognizes the criticality of providing support to the
  ground forces. Available air support is assigned missions according to the
  following categories of requests: preplanned, on-call, and immediate.
  Preplanned
  8-29. A preplanned mission is a mission planned well in advance of its execu-
  tion, usually 24 hours prior to launch. Such missions are normally planned
  against static or non-moving targets with known locations.
  On-Call
  8-30. An on-call mission is one in which the target may be predesignated,
  but the timing of the attack remains at the discretion of the ground force
  commander. These missions are normally planned to support maneuver
  forces not yet in contact with the enemy, but expected to make contact
  once the aircraft are available. The on-call mission is planned the same as
  preplanned missions, with the exception of the attack’s timing. A “window of
  availability,” usually no longer than 4 to 5 hours, is established. The mission
  can be launched at any time during that window. On-call missions are
  planned with secondary targets in the event the window of availability
  expires before the primary target becomes available for attack.
  Immediate
  8-31. The OPFOR designates a limited number of aircraft to respond only to
  requests from ground commanders for unplanned immediate air support.