Probably long gone, since the introduction of various service charges, taxes and fees, are the days of totally free (ID100) interline staff travel tickets. The Interline Secretary of airline A would forward a letter to their opposite number at airline B, requesting a ticket and promising reciprocal benefits to that airlines employees. I enjoyed many a free trip in the 70s and 80s, always on a standby basis, but often with upgrades. Most memorable being LHR-LAX-AKL all the way in F on NZ, and a last minute upgrade into seat 1A on a TWA 747 JFK-LHR.
Another thing that probably happens much less these days, is people being rather impressed and maybe a little envious, upon hearing that you work for an airline.