Error codes in FlightXML 2

FlightAware AeroAPI
1

So I call some entry points and get

{"error":"NO_DATA unknown airport INVALID"}
{"error":"NO_DATA flight not found"}
{"error":"INVALID_ARGUMENT endDate is too far in the future (12 months)"}

This makes sense. NO_DATA returned for valid arguments but no data . INVALID_ARGUMENT when the arguments are bad. However, I call InboundFlightInfo with valid faFlightId and no match I get:

{ "error":"INVALID_ARGUMENT Inbound flight is not known"}

My code was expecting NO_DATA here since the argument was valid. Seems odd. If I do pass an invalid faFlightId I get what I expected:

{ "error":"INVALID_ARGUMENT: invalid {faFlightID}"}

Is there any docs on error codes?