It is definitely free, but ever since Boeing announced disconnection, the reliability has been highly variable. On my SQ flight FRA-JFK a few days ago, it said "Service Temporarily Unavailable" for the entire flight. Same for a recent LH flight FRA-DTW. A recent FRA-DFW worked for the first few hours and then went unavailable. It did work on a DXB-FRA flight a few days ago as well as on a recent BAH-FRA flight. Bottom line... you can't count on it working.