So with 4 aircraft on a typical days schedule, how many crew are rosteded on for a given day and how many are on standby. If its only one on standby then it would only take two to go sick before this situation occured.
Also if the crew were CHC based were they earthquake affected. NZ apparently replaced some Atr-72 services with 733 because of a shortage of Atr-72 crew who are CHC based.