A flight to be conducted in accordance with ETOPS procedures shall not be commenced unless, during the possible period of arrival, the required alternate aerodrome(s) will be available and the available information indicates that conditions at those aerodromes will be at or above the aerodrome operating minima approved by the authority for the type of operation.
Adequate Alternate Aerodrome
An adequate alternate aerodrome is one at which the landing performance requirements can be met and which is expected to be available, if required, and which has the necessary facilities and services, such as air traffic control, lighting, communications, meteorological services, navigation aids, rescue and fire-fighting services and one suitable instrument approach procedure.
Suitable Alternate Aerodrome
A suitable alternate aerodrome is an adequate aerodrome where, for the anticipated time of use, weather reports, or forecasts, or any combination thereof, indicate that the weather conditions will be at or above the required aerodrome operating minima, and the runway surface condition reports indicate that a safe landing will be possible.
Source: ICAO
See also:
Adequate ETOPS en-route alternate aerodrome
Approved one-engine-inoperative cruise speed
ETOPS (Extended range operations for two engine aeroplanes)
ETOPS area
ETOPS planning minima
Types of ETOPS En-Route Alternates