Here are four hot springs that you can land a plane within easy walking distance of:
30 miles North of Fields, OR
ALVORD: N42,32.640, W118,32.016 This spring is on the edge of a six by twelve mile dry lake. The biggest airstrip you ever saw. Well maybe not, but be carefull to only land when it is really dry. In the winter, it is frequently covered with shallow water, and even after the water dries up in the summer, the mud can swallow all sorts of vehicles. The spring is on private land, but the public is allowed to use the concrete soaking pools. The road has power lines along it, so I can't recommend that.
15 miles WNW of Denio, NV
BOGG: N41,55.332, W118,48.099 This spring is more "wild", but a great soak. You can land on the gravel road to the East of the springs.
20 miles SSE of Fields, OR
WILLOW: N42,16.528, W118,15.919 This spring has a nice pool to soak in and an outhouse. Land on the dirt road. The road can be very muddy after a rain, and there will be ruts. Watch those long props.
60 miles WSW of Denio, NV
DOUBLE: N41,03.039, W119,01.627 This spring has a nice metal watering trough for a tub. You can land on a short stretch of dirt to the north. Again, muddy after a rain.
tom