This is a very specific player issue you are dealing with. JW Player is correct, the HLS url is "supported in desktop browsers and natively supported on both iOS and Android." For now, I would test the actual HLS url and drop the <?php echo $flightId?> piece of your call to see if this is the issue within JW Player.
If you can setup this simple test below with your latest version of JW Player, only using the HLS url and playback successfully, you will know that the issue lies with JW Player handling the variable in the url.
I hope this helps.
<script>jwplayer.key = "[jwplayer-key]";</script>