What must all IR operations be conducted on in terms of flight plans?

IR operations, which refer to Instrument Routes or Instrumented Flight Rule operations, must be conducted on IFR flight plans or through approved Altitude Reservations. This requirement is grounded in the need for maintaining safe and efficient operations within controlled airspace. IFR flight plans ensure that aircraft can be guided safely by air traffic control under varying weather conditions, particularly when visibility is limited.

Using IFR flight plans establishes a set of procedures and routes that enhance predictability and safety. These plans allow for standardized navigation and communication protocols among pilots and air traffic controllers, which is crucial during military operations where coordination is key. Approved Altitude Reservations further ensure that military operations can be conducted at designated altitudes without conflict with commercial or civilian air traffic.

In contrast, the other options, such as VFR flight plans or visual flight plans, are more adaptable to good weather conditions and do not provide the same level of structure or safety as IFR flight plans, particularly in the context of military operations where precise control of airspace is vital. Basic flight plans may lack the specific requirements needed for operational readiness and safety inherent in IR operations.