Certain airlines like USAir use chimes to indicate FAs to be seated (or at least USAir did pre merger with America West) and others like AA have no indication that FAs are to be seated (just an announcement to prepare the cabin for landing). Interestingly, AA does use chimes to indicate entrance onto the runway. On AA, never saw FAs still up and about upon landing although one night at JFK they sat down within less than a minute from landing.