Lookin for some honesty from some older members and lurkers. Chem/con-trails.

I remember growing up near the rural areas in South-central Pennsylvania in the 1970s, and the farmers on the TV farm reports lamenting the fact that the popularity of airline travel is causing more cloudy days due to persistent contrails that spread out to become cirrus clouds (farmers for the most part like clear sunny days). I'm not sure if it was part of the farm report or part of a farmer's "Public Service Announcement", but I remember it.

Here is something that is even better than memory -- a paper published 40 years ago indicating that spreading and persistent contrails are not a new thing...


Linked below is a research paper published in 1972 that discusses long-lasting contrails that can spread out into clouds:

Measurements of the Growth of the Ice Budget in a Persisting Contrail
(Note: This links directly to a PDF file)


Here is an excerpt:

...Under favorable conditions, a lateral spread of kilometers is observed with presumably comparable vertical spreading. If sufficient air carrier traffic exists, an entire overcast of contrail cirrus may develop and persist for hours with rapid growth in ice budget in individual contrails...

So it seems from this paper that long lasting contrails that spread out to create overcast skies was something that was happening at least several decades ago.

reply to post by Jazz87


I am 21, So born in the 90's.... I remember them, but not lasting as long as they do now. It seems that they are getting Longer/Thicker too. When I was a kid they would be 20 ft. from the plane, than vanish... and there would be a 20ft trail following the plane.. but now they stick around forever (:

^^ me too!

I dont fly often but I don't remember the ever pumping some type of cold steam into the cabin like they did on a recent flight I took.. Could they be spraying the passengers too!?! Here's a video I took-
www....(nolink)/?lxe7f24lcdd4sk8

reply to post by abcd123420


That's probably just the AC condensing. Was it on a hot and humid day at the start of the flight?

See example:

Thanks i didnt know wtf it was lol.. I wonder if they put something bad in it?

reply to post by abcd123420


Nah, it's just the moisture in the air. There's high humidity, say 80%. But when temperature falls, the air can not hold as much water, so the relative humidity rises to above 100% and so the water in the air condenses out, and then as the cold air mixes with the warm cabin air, it quickly evaporates as the mixed air temperature rises.

It's kind of like breathing out on a cold day, except in reverse - the plane is like your hot muggy lungs, and the ac is like the cold air coming in.

Most of the water will condense around the AC coils, and drain away, so the air in the plane will get less humid. This is why you get water dripping under your car after driving with the AC on a hot day.

It's kind of interesting, as it relates to how contrails form.

reply to post by Uncinus


Yep - as an aircraft mechanic working on the "ramp" I used to see this a lot in summer months - the air-con would be turned up high (so as to cool the air down a lot), and with high humidity the moisture removal system wouldn't be able to cope with the amount of moisture, so the vapour would come out the vents - and disappear quickly into the warm air inside the aircraft.

Aircraft airconditioning is a bit different from your home variety - at home (well at least at my home!) the aircon works by cooling a working fluid, then passing the air inside my house over that fluid to cool the air down (or heating up the working fluid to provide warmth in winter).

An aircraft system works by taking air from the engines and cooling it down then passing it into the cabin. When the engines are not running it just takes outside "ambient" air - so if it is hot and humid outside the aircon has to work a lot harder.

And of course with doors open for servicing and pax/crew entry the cool air never actually stood much chance of cooling the aircraft down significantly at all!!

Originally posted by abcd123420
Thanks i didnt know wtf it was lol.. I wonder if they put something bad in it?

Now come on, why would airlines be trying to poison their customers? some of you take paranoia to absurd levels

reply to post by Uncinus

I was a passenger on a flight out of Washington DC just last week where there weather was extremely hot and humid, and the plane's auxiliary power unit was not working (the power unit that powers that plane while at the gate with the engines off), so without air conditioning it was very hot and humid in the plane while the passengers were being loaded on...

...When the plane's engines finally started and the air conditioner turned on, the foggy air coming from the air vents looked like something from a dry-ice fog machine at some sort of rock concert.

I fly enough to know what it was and had seen that before on several occasions, but this was extra thick due to the extremely humidity conditions. I remember thinking to myself that the plane could be on fire and we wouldn't even know it. Although it was nice to finally have the air conditioning on.