A flight shall not be commenced unless, taking into account both the meteorological conditions and any delays that are expected in flight, the aircraft carries sufficient fuel and oil to ensure that it can safely complete the flight. In addition, a reserve shall be carried to provide for contingencies. When a destination alternate aerodrome is required the following have to be fulfilled:
Either to fly to the alternate aerodrome via any predetermined point and thereafter
• for 30 MIN at 450m (1500ft) above the alternate aerodrome, due provision having been made for an additional amount of fuel sufficient to provide for the increased consumption on the occurrence of any of the potential contingencies specified by the operator to the satisfaction of the State of the Operator;
• provided that fuel shall not be less than the amount of fuel required to fly to the aerodrome to which the flight is planned and thereafter for two HRs at normal cruise consumption.
Or to fly to and execute an approach, and a missed approach, at the aerodrome to which the flight is planned, and thereafter:
• to fly to the alternate aerodrome specified in the operational and ATS flight plans; and then
• to fly for 30 MIN at holding speed at 450m(1500ft) above the alternate aerodrome under standard temperature conditions, and approach and land; and
• to have an additional amount of fuel sufficient to provide for the increased consumption on the occurrence of any of the potential contingencies specified by the operator to the satisfaction of the State of the Operator.
Source: ICAO Annex 6