TopBunk
Not in the regulations, but in the operations specifications issued by the FAA to all aircarriers. Therefore, if specified therein, crews must divert unless the alternate is below landing minima, or forecast to be so at time of arrival. If the long range flight is operating under re-release, a different alternate (or two) may be specified in the re-release dispatch message.
To be caught short is not good, as Avianca has found out.
QF and MH have had rather close calls at LHR as I recall....ie: little fuel left in tanks at the parking bay.
