Although passengers might survive a crash, can you imagine what it might be like encased in foam and trapped in a fuselage in the middle of a forest or desert or floating in the ocean hundreds of miles from civilization? Perhaps cyanide filled dentures might be useful there.

According to statistics I've seen, more people die in burning planes on the ground because they can't get out in time than are killed during the crashes. The foam would obviously compound this problem.

Hmm, this sounds a bit over the top. I would perfer to have an old fashion parachute that would separate from the wings, and the rest of the fuselage, and glide gently down to earth. Being encased in aerosol foam with 15000 gallons of jet fuel igniting around me does not sound like a way I would perfer to die.

The ideal shock absorber would be to fill the cabin with water and give the passengers breathing apparatus. Unfortunately this would make the plane so heavy it could never fly.

Interesting idea but remember the plane is traveling at 500?? mph. So the instant seat 5B hits earth (and slows to 0 mph rather quickly), right behind are seat rows 6 through 27, two lavatories and a tail section that are still traveling at 500 mph (i.e. 5B and 27B and all in between will kiss in less than 1/7 of a second). All of them will be joining 5B in 4B's seat back. Foam inside a plane will not stop the inertia. Alternatively, we could fill the earth with foam - that would allow a crashing plane to decelerate at a survivable rate. Until we do that, I'll go for the parachute bkeene12 recommended.

What you're talking about here sounds more like the need for a system to deploy airbags that stay inflated until the plane quits moving. Seems great as long as the fuselage remains intact. Pretty much useless otherwise.

Whataloadof: Excellent idea.
The foam already exists on most aircraft, it exists as the seats we sit in. If the seats were contoured to our bodies and the seat in front of us matched our contour, then the seats just need to slide together to encase us in foam. If the aircraft computer/sensor package detected an impending catastrophic accident, the seats could slam together, jetison from the plane, and deploy a ballistic parachute to allow most passengers to survive.

The foam system may not be suitable in all situations, however, computers and sensors are commonly utilized for making such decisions. Airbags in automobiles are typical. Only under specific circumstances do airbags deploy.

Also, the foam does not necessarily need to be a solid. Aerogel is a lightweight compound that resists deformation, but it certainly can be deformed easily. How many G's can be experienced and survive with the right density of material? There is so much that is unknown about this problem that it we can only come up with ideas for what might work, or what possibly should be considered.

A professional skydiver jumped at 3,000 feet AGL and both chutes failed to open. With a terminal velocity of about 150 mph, the skydiver landed flat on his back on newly layed sod. After a short time the skydiver was conscious and aware, but was unable to move having broken many of the bones in his body. He walked out of the hospital after 6 months and returned to skydiving. With some assistance, even catastrophic accidents may be survivable by many, though probably not all.

Excellent Idea