Modern CNS (Central Navigation Systems) use clusters operating in UTC domain. It is requiring synchronization accuracy better than a millisecond. For an airplane flying at a speed of about 1000 km/h, the synchronization ERROR of single second defines a position error of 300 meters.A Voice Control Systems (VCS) require trusted timestamping to store pilot voice and telemetry flight data proving event chronology and non-repudiation. A UTC leap second support is essential.
Please consider to use min. 1 – best if 2 redundantly operating time servers per single Data Center. Server can be configured on way of giving a ref. time to each other. Servers can be equipped with redundant powersupplys.
A very good idea is to use 2 redundant GNSS receivers. Two antenna-receivers helps prevent GPS jamming and spoofing. They can be installed on location 700 meters from time server each.
non-repudiation & data integrity
crypto timestamping RFC 3161