Division NCO.OP.140 Destination alternate aerodromes – aeroplanesF1F2

For IFR flights, the pilot-in-command of an aeroplane must specify at least one destination alternate aerodrome in the flight plan, unless the latest available weather information for the destination, for the period from an hour before the ETA to an hour after the ETA or the period from the actual time of departure to an hour after the ETA, whichever is the shorter, indicates that there will be a ceiling of at least 1000 ft above the DH or MDH for an IAP and a visibility of at least 5000 metres.