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IFR flight planning

IFR flight planning is the process of preparing a flight to be flown under the instrument flight rules: choosing a route and minimum levels, nominating departure, destination, and alternate aerodromes, computing fuel, and confirming the forecast weather meets the applicable planning minima. In UK and EASA airspace the rules differ by operation type, with Part-CAT (commercial air transport) and Part-NCO (non-commercial, other than complex) carrying their own aerodrome operating and alternate planning minima.

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UK CAA IFR Flight PlanningHow to plan a flight under the instrument flight rules in the UK: the IFR, Part-CAT and Part-NCO weather minima, alternate selection, and planning minima.

Frequently asked questions

What are the instrument flight rules (IFR)?

The instrument flight rules are the rules under which an aircraft is flown by reference to its instruments rather than by visual reference to the surface. In UK airspace they derive from the Standardised European Rules of the Air (SERA), retained in UK law, and they govern minimum levels, cruising levels, separation, and the clearances required in controlled airspace.

What is the difference between Part-CAT and Part-NCO?

Part-CAT (Annex IV of the Air OPS Regulation) governs commercial air transport operations. Part-NCO (Annex VII) governs non-commercial operations with aircraft other than complex motor-powered aircraft, which covers most general aviation. The two annexes set different aerodrome operating and weather planning minima, so the regime that applies to your flight determines the minima you plan against.

What weather minima apply when planning an IFR flight?

Planning minima decide whether a forecast allows an aerodrome to be used as a destination or alternate. They are based on the forecast visibility or RVR and cloud base set against the minima for the available instrument approach, and they differ between Part-CAT and Part-NCO. An alternate normally has to be nominated unless the destination forecast is sufficiently above the applicable minima for a defined period around the estimated time of arrival.

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