I was fortunate enough to see an Osprey right above the house yesterday before it climbed up into the stratosphere. While it was gaining altitude it would hover in place flapping its wings as if it was getting ready to dive into the corn field below it, then it would drift lazily along circling and climbing and then do it again. I convinced myself, right or wrong, that the bird wasn't hunting, but more likely trying different vantage points to see where it's mate and/or offspring were (I heard it calling a few times and that's where my mind went). If I had of watched things in reverse order and saw a far off bird circling and occasionally kiting over the corn fields, I would not have thought of Osprey as a possibility just because of behavior, or more accurately, because of the location of the behavior. What the bird was doing wasn't really unusual, if it had been flying over, or near the river and not over the corn fields running parallel to the river.
So yeah, I've seen Osprey circling lazily on the thermals and ride the currents without much flapping at all. Yesterday's sighting involved some flapping but there was just as much flapless gliding and circling going on too. While none of them compare to Turkey Vultures, I suspect that most raptors take advantage of floating/circling on the currents, both to gain altitude on the thermals and to slowly scout out a large area for prey, predators, and especially at this time of year, maybe even checking up on their mates and offspring.