Summary: The Scheduled Flights by Route API is for non-stop and direct (one-stop) flights. The Connections API is up to two-stops and includes some additional filters for freight-forwarders and cargo handlers. A common successful pattern is to first use the Scheduled Flights by Route API and then, if it does not return the results you are looking for, follow it up with a Connections API call for the same route.
More details about each product are included below.
Scheduled Flights by Route API:
The Scheduled Flights by Route API provides access to the schedule information for upcoming flights. It is designed to work in conjunction with the Flight Status API to provide continuity between scheduled flights in the future and real-time flight data in the present. It allows convenient search methods by flight, route and airport. We use raw schedules to inform the creation of flight records. This data is loaded daily and is normalized to make it easier to match flight schedules to available operational flight data. Minor updates to a flight schedule may be applied directly to a flight record to improve flight matching.
FlightStats is trying to flexibly match the operational flight data from over 500+ data sources with the published flight schedules. Business rules are applied in a specific way for this use case. These business rules include but are not limited to mapping codeshares, wetleases, etc.
The Connections API provides access to information on upcoming connecting flights between two airports with up to two-stops. A good example would be to find various ways to fly from a smaller, regional airport such as Fort Lauderdale, Florida to a final destination such as Portland, Oregon. The Scheduled Flights by Route API will not return any results for this type of request if there are no direct flights between two airports. However, the same request given to our Connections API will return a variety of options. The Connections API will return direct flights when available, followed by connecting flights with stops. The data payload returned for this API is a list of schedules, with extensive detail including departure and arrival times, code share information, carrier, flight number, equipment type, and number of stops and is updated daily. In addition, the payload includes the elapsed time for a given connecting schedule. The score indicates how well each flight fits the requirements you specify in your Connections API request. It is based on weighted parameters, filtering options and connection logic controls, with a higher score indicating a route that better matches your needs relative to other alternatives. The Connections API has variable response times depending on the complexity of the search pattern and the number of possible routes that can fulfill the request.