'flight not found' with info from previous API call

I need to get flight (or flights) by user-provided information:

  • airline iata/icao code
  • origin iata
  • destination iata
  • datetime of departure

I find my flight with this information by traversing results of successful AirlineFlightSchedules call. Now I want the flight info. But when I try to use GetFlightID or FlightInfoEx with previously obtained ident and departure time I get ‘flight not found’. This is weird since I’m using presumably correct data retrieved from AirlineFlightSchedules.
Am I doing something wrong? Thanks for help

Flights are only trackable by FlightInfoEx (or GetFlightID) when it is close enough to departure, usually < 24 hours but it may vary depending on the airline and/or area of coverage.

You may need to use FlightInfoEx with just the ident (airline + flightnumber) since the filed_departuretime of the flight may not always match exactly the departure time that is published in the schedules returned by AirlineFlightSchedules, and then programmatically browse through the resulting flights to find the closest to the one you want.

The problem is, we don’t know the flight number. We would like to find the flight by the information above (which, by documentation, should be possible with those two API calls).