No that’s not the level of ascent, but the absolute altitude. You will recall that as you get higher, the air pressure drops. That makes it a real pain in the ass to fly planes. So by the time you are up to about 14000 ft, you have only ~70 % of atmospheric pressure. That’s 30% reduction in thrust, and lift. It also changes the stability and handling characteristics of the plane.
So it was with an element of trepidation that I decided to fly the plane at 5000 feet (previously only flown at sea level), on the shoulder of mount Shasta, a 14000 ft extinct volcano in northern California. The conditions were perfect (dead calm, good lighting), however the terrain was not. Trees everywhere. Trees have a habit of reaching out and ‘grabbing’ rc planes. What it really is of course is the plane is quite small, and so distance is really quite hard to judge, y’know ‘will the plane fly in front of that tree, or into it?’ Keep ‘sky’ behind the plane is usually a good, if hard rule from keeping your plane from the clutching branches of the trees. However the flight went pretty much perfectly. I really used the headset for the first time, although as with everything there are always unforseen teething troubles. In this case it was, as my head looked upwards to see the plane, it moved the headset so I could no longer easily see what was happening on the plane. And yeah, when in flight, you really don’t have the luxury of ‘ooh, I really think I need to adjust these straps a little! The plane flies at ~20 mph, and at that speed it can be real easy to lose ‘orientation’ on the plane.
Flight was pretty!

Upper frame, Mount Shasta, from the air! It's still over 2 miles above you at this point. Lower panel, that's MEEE, from the air. 🙂
Anyways, it was a very ‘buzzzzzzzzed’ Tfoot (shaking hands etc), who once again managed to get his plane back to the road clearing where he had taken off from!