Isaac Asimov says the following is the quintessential joke -
“You know, I haven’t heard from Irving for some time.”
“Gee, didn’t you hear? He fell off a third story balcony and landed on cement. Broke his back, both legs, and they say he will probably be a vegetable for the rest of his life.”
Water isn’t a good thing to land on if you fall from a great height. Water is ok up to maybe 50 feet or so, but around there you start to see some injuries, depending on how you hit the water. The percent of injuries gets higher as the height goes up (as you’d expect) and by the time you get to the height of the Golden Gate Bridge (about 200 feet) it’s almost always fatal. I don’t know of anyone who has fallen from a really great height (several thousand feet) who landed on water and survived.
Snow is probably your best bet. Vesna Vulovic landed on snow. Ivan Chisov (mentioned earlier) hit snow and also landed on the side of a steep slope. Olen Cooper Bryant and Arthur Frechette (two other guys during WWII who basically got shot out of their planes) both fell over 10,000 feet and landed in snow and survived.
Evergreen trees aren’t so bad either. Nicholas Alkemade (mentioned earlier) landed on trees, thick brush, and a few inches of snow. He probably has the most amazing story because he basically was able to just get up and walk away after his fall (all he did was sprain his knee). He’s the only one who didn’t spend months or even years recovering from his fall. Paddy McGarry was another one from WWII who fell over 10,000 feet and survived. He also landed on fir trees.
The only one I know of who really fell a great distance and didn’t land on either fir trees or snow was Alan Magee. He basically fell 20,000 feet and landed on the roof of the St. Nazaire train station. It’s not clear if he hit the skylight directly or if he hit the roof and bounced and fell through the skylight. Either way he didn’t exactly land on something soft. Alan was unconscious at the time so he couldn’t say exactly how he landed either.
In the 50s or 60s, a candidate for suicide survided after jumping from the Eiffel Tower in a similar way, by landing on a car that was totalled.
So, it seems there are numerous instances of survival after a fall from high height. You just have to be extremely lucky (or maybe unlucky, likely ending up seriously wounded on top of whatever made you attempt a suicide at the first place).
As for the stewardess, frankly, I’m not sure that being inside a part of the fuselage makes her survival less impressive. Fuselages aren’t devised to protect from harm people falling from the sky.
Spruce and fir trees are ideal for this: they have dozens of thin, springy, horizontal branches on top of each other, all the way from the near-ground to the near-top, like a 100 ft. bed of leaf springs. I can’t think of a better natural “surface” to land on. Pine trees are bad news, since once mature they have no lower branches and the upper branches are thick, strong and inelastic, as with most broadleaf trees.