IFR
Alternate aerodrome requirements
Destination alternate
- Required unless destination weather is forecast to remain at or above planning minima around the ETA, the destination has an instrument approach procedure (or is otherwise suitable), and no other operational reason requires one.
- To be used as an alternate, forecast weather at the destination alternate must be at or above the applicable alternate minima at the estimated time of use.
Take-off alternate
- Required when weather at the departure aerodrome is below the applicable landing minima, or when it would otherwise not be possible to return there.
- For helicopters, normally selected within a limited distance or flight time of the departure point, as defined in the operator's operations manual.
Isolated aerodrome
- A destination with no suitable alternate is treated as an isolated aerodrome for fuel planning purposes.
- Instead of standard alternate fuel, extra fuel is carried to cover a defined additional holding/diversion contingency.
Source: EASA Air Ops – Part-NCC/SPA – Alternate aerodrome selection & fuel policy