Park at the turn of the approach road; walk into the woods (you will see a sign that says "thin air trail". Approach for about 5-10 minutes, climbing steeply left along the base of the wall until you clearly see a two-bolt anchor and a flake leading to it beginning about halfway up; this is the beginning of the route.
Thin Air is a classic route at Cathedral and on weekends expect to wait in line.
Pitch 1: Begin either straight up (5.5) or left (5.3) up to a ledge, following it right for a few meters. Continue straight up a flake system with angular blocks (5.5) to a two-bolt anchor. About 50 feet.
pitch 2: (can and probably should be combined with p1 unless the second belay is taken). Traverse right from the anchor along a natural weakness, clipping 3 fixed pins along the way. One slightly tricky 5.6 move is the psychological crux of for many people. Belay at another bolt anchor. About 70 feet.
Pitch 3: up slabs with decent holds to a beatiful flake, following it into a short chimney with a tree somehow growing in the middle (talk about BOMBER pro); exit the chimney on the right onto a great ledge and belay at another bolt anchor. (5.5, 70 feet) I spent 4 hours here one time as a "fixed" belayer for a kids' climbing group and loved every minute of it.
pitch 4: the longest and in my opinion the best pitch of the route. Straight up the crack system from the belay on good holds until you reach a small overhang (fixed pin). Slightly left and layback up a flake (crux; 5.6), across a ledge and then slightly rigth again until you reach trees; belay at tree anchor with slings. 130 feet.
pitch 5: short scrample up roots and dirt to the large ledge from which you can walk off, or if you're looking for a challenge you could try the rather smooth slab to the right (runout) which is about 5.8, but this isn't really part of the route. About 50 feet.
Normal rack. All kinds of protection exists here but it is all very good.
If you have information about this route that doesn't pertain to any of the other sections, please add it here.