what does it mean by flagging or unflagging airline routes. i haven't understood the concepts clearly.
You'll get more answers posting in the General forum, not the Off-topic forum.
https://www.airwaysim.com/forum/index.php/board,1.0.html
But to answer your question, flagging routes doesn't do anything except put them at the top of the sort order on the Manage Routes screen. Supposedly it turns the background another color but like many other users, I can't see the difference.