"Gordon" wrote:
I have experimented with plastic and found the corkscrew part of coke
bottles very strong and cheap plastic

It's strong *for plastic*. It's vastly weaker than any aeronautical
structural material, like aluminum, titanium, or carbon graphite.

if the plane crashed
it would not disintegrate or catch fire and if it crashed at sea it
would float and could be towed back to land by a ship.

Since plastic is weaker than structural metals, a plastic plane would
disintegrate even worse (or earlier) than a conventional aircraft during a
crash. It would also burn more vigourously and loose strength as it heated
up.

http://www.scaled.com
I came across this composite plastic website who make small plastic
planes and who made the composite plastic space shuttles for Richard
Branson.

Scaled Composites is very very good at compsite prototypes (primarily aramid
and carbon composites). Until recently, it was cost-prohibitive to use this
technology for mass production of large aircraft. Boeing's 787 and Airbus's
A350XWB will both make extensive use of composites. Don't forget though,
it's the fibers, not the plastic, that gives you most of your strength.

Tom.