From the FAQs:
FA may not be getting data from a flight outside the service areas.
How does FlightAware handle flights around the world? What is FlightAware’s service area? (Back to top)
FlightAware’s primary service area includes airspace operated by the United States (including Alaska, Hawaii, Puerto RIco, and Guam), Canada, the Caribbean, Australia, the United Kingdom, and France. Flights in the primary service area support real time maps, departure and arrival information, delays, and more.
FlightAware’s secondary service covers scheduled major airline operations at any airport in the world. Flights in the secondary service area support departure and arrival information. Secondary coverage areas may have real-time positions for ADS-B equipped aircraft operating in FlightAware’s ADS-B coverage area. Additionally, some airlines send FlightAware satellite position reports from aircraft worldwide that augments other position data and provides transoceanic coverage as well.
For flights arriving in a service area from outside of a service area, FlightAware will be able to track the flight when it nears a service area. For flights departing a service area, FlightAware will be able to track the flight until it leaves the coverage area. Flights may not be tracked beyond that point unless they enter another service area.
Not all worldwide data sources (e.g., European data, datalink ARINC/SITA ACARS, etc) are freely available on FlightAware.com due to government regulations or commercial arrangements. You can contact us if you have a commercial need for worldwide data.