Final answer:
Airfields listed as Official Business Only or Prior Permission Required can be used as alternates for IFR flights, but there may be additional requirements or restrictions.
Step-by-step explanation:
Airfields listed as Official Business Only or Prior Permission Required can be used as alternates for IFR (Instrument Flight Rules) flights, but there may be additional requirements or restrictions in place. Official Business Only means that the airfield is primarily used for official government or military purposes, but private aircraft may be allowed to use it with prior approval. Prior Permission Required means that pilots must obtain permission from the airfield owner or operator before using it as an alternate.
For example, an IFR flight plan might include an alternate airfield in case the intended destination becomes unavailable due to weather conditions. If the alternate airfield is listed as Official Business Only or Prior Permission Required, the pilot will need to contact the airfield and obtain the necessary permission or clearance before diverting to that location.