8.2. General. If possible, start mission preparation several days before departure. Destinations and routes may be selected any time in the planning process; however, dynamic flight planning tasks, such as wind computations, fuel calculations, and weather briefings, must be completed shortly before departure. Note the distinction between IMC and IFR. IFR and VFR refer to rules and procedures while IMC and VMC refer to meteorological conditions. VMC generally refers to the ability to fly using references outside the aircraft while IMC generally refers to conditions where instruments inside the cockpit are used as the primary references. Conditions must generally be VMC to fly using VFR, but conditions can be either IMC or VMC to fly using IFR. Although there are differences between IFR and VFR flight, there are common planning steps and tasks. The following general guidelines apply to the planning and execution on any type of navigation mission.

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