Now, the simple loop on the end of a flying line is fine for small kites, where the line usually has ample strength. However, for much bigger kites, it's a good idea not to weaken the line unnecessarily. In particular, there are 2 knots which offer greater strength than the simple Loop - the Double Loop and the Figure Eight knots.
If you're in the habit of using a Truckie's Knot to pull some bow into a spar, then of course, that uses the Loop Knot as well. No need for anything fancier there.
The Dowel Sode uses 2 long loops of flying line to tension the bowed horizontal spars away from each other. The simple Loop is adequately strong in this situation too.Now, if you really want to go overboard with knot-tying...
The Double Loop is significantly stronger than the Simple Loop. That is, it does not weaken the breaking strain of the line as much. However, it's almost as easy to tie as the Simple version. Just wrap the loop around twice instead of once. That's it. Use this knot on the end of your flying line, so it can be attached to a kite bridle with a Lark's Head.
This knot is also worth remembering whenever you want to tie a large knot that will not pull through another knot. For example, near the towing point of a keel. Or perhaps to make completely sure a Slip Knot doesn't slip undone! In both those cases, the Double Loop looks neatest when the loop is tied as small as possible. After all, the loop itself is not being used for anything.
A double-ended flying line would also come in handy for attaching 2 kites together in a train. If the kite closest to ground had a short line out the back, with a large knot, the line to the second kite could just be Lark's Headed on. Quick and simple.
The Figure Eight Knot is another loop variation which is significantly stronger than the Simple Loop. It's a fishing knot, and just a little trickier to tie.
Many kite people use this knot on the end of their flying lines, which is then Lark's Headed to a kite's bridle. One day I'm going to get around to doing some tests to see if it really is stronger than the Double Loop Knot. The results will be reported on this website!
I suppose the Figure Eight could be used as a large terminating knot like the Double Loop, but the latter is much quicker and easier to do.
How about a loop tied into both ends of the flying line? Like the Double Loop, the Figure Eight could then be used for tethering a kite to a ground stake. Just by slipping the loop over, as long as the stake was shaped or angled to ensure the loop doesn't slip off.
Also, with the right bridles, flying lines with a loop knot on both ends could be used to hitch together a train of kites.