The 'IsFlightRulesVisibleAndMandatory' setting adds a new drop down box to the Create order screen for both the arrival and departure. In this box the flight rules (VFR / IFR) applicable to the leg can be selected.
Contrary to the setting name, the flight rules box is not mandatory to fill in when creating an order.
This field is only for record keeping or reporting to the required authorities. Prices and surcharges cannot be currently based on the flight rules.