AFAIK, contrails have little to do with pollution, but depend only on
the amount of water in the engine exhaust, which should be pretty much
a constant per mass of fuel consumed. I suppose that particulate
matter may be needed, too, to form the contrail, but somehow I think
there is probably always going to be enough of that.

Sean


On Wed, Jan 13, 2010 at 9:18 AM, Carl Denk <cdenk@windstream.net> wrote:
> Actual I have noticed in recent years less contrails for whatever
> reason, I suspect improved engine technology with better fuel economy
> and less pollution.
>
>
>> One only needs look at films of B-17 bombers
>> flying at 20+ thousand feet during WWII to see that this is not a a new
>> phenomenon.
>>
>> Vic
>>
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