Why are the actual arrival/departure times missing on an international flight?

If no actual departure or arrival information is present in our system it just means that our data sources have not confirmed these details.  If the final flight stats cannot determine the final status of a flight from a Data Source in a reasonable amount of time the flight will marked as status "Unknown" in our system. 

FlightStats aggregates data from many sources to provide more complete coverage of global commercial airline flights than anyone else.  Our aim is to provide a consistently excellent service with nearly complete coverage in all countries, and our coverage is always increasing. However, there are problems finding reliable sources of real time flight status data for some of the major and minor carriers in Asia, Africa, Latin America and the Middle East.