OBS_VALUE: The number of foreign registered aircraft operated by an air operator certificate  (AOC) holder must not at any time exceed 25% of the total number of aircraft operated by the AOC holder.Unless the Director‑General of Civil Aviation otherwise permits, an AOC holder must — (a) operate at least one Singapore registered aircraft for each aircraft type operated; and (b) have management and operational control of at least one Singapore registered aircraft at all times.