I personally have been paid to fly aircraft that “sprayed” stuff in the air at mid to low altitudes and can say at least from my experience there is no mysterious chemicals or unknown toxins spewed from aircraft. Aerosol charges of silver iodine (Agl) and carbon dioxide with liquid nitrogen generators are dropped out of an aircraft into clouds or even sometimes in an area someone would want to try to get a cloud to form (i.e. farmers who desperately need a nice rain cloud over their fields). It amounts to a big firework with liquid nitrogen to rapidly cool the air in an effort to cause clouds that wouldn’t normally rain, to rain; and clouds that would rain, to possibly rain even more. These charges sometimes leave a trail of smoke, but nothing like the photos associated with “chemtrail conspiracies”. It ends up looking like a streak of smoke and dissipates very quickly.

Silver Iodine is a solid yellow inorganic compound often used in photography and as an antiseptic in medicine. Now if you want to get excited over “conspiracies” there are some groups out there thinking Silver Iodine is possibly toxic. Kind of hard to believe when it is not scientifically proven to be toxic in addition to its wide use in medical applications.

Those are the only “chemicals” I’ve ever put in the air, and you’d be exposed to far greater dangerous chemicals while riding in your car in the city, or eating out of a plastic microwavable dish.

Besides – if the government has some huge top secret program costing billions to spray spooky chemicals in the sky all over the world, do you really think someone who knows is going deliver some sort of earth-shattering expose here on Y!A to you and your inquiry?

First off the reason that some jet’s leave contrails while others don’t is simply due to the fact that temperature various at different altitudes and areas. So two jet’s heading North at the same altitude some 10 miles apart you may see one is producing the contrail and the other is not.

Now what is a contrail? A contrail in the condensation of the extremely hot air coming out of a jet engine, thus producing thrust. It’s kind of like when you leave a glass with ice out for a bit and you get the water buildup on it. Chemtrails are simply made up items of people who are simply bewildered as to why an airplanes wings don’t need to flap in order for it to fly…

http://www.youtube.com/watch?v=65KLN5gDHzI

Oh, but you are talking about contrails because there is nothing else.

The trails you see are condensation trails (contrails). They consist of water. Water vapor is produced by jet engines (along with carbon dioxide) in their exhausts. As it leaves the engine, it’s an invisible gas, but if the air around the airplane is cold enough, the gas condenses into liquid water droplets or ice crystals, and this forms a visible cloud that trails behind the airplane.

Whether or not a contrail remains visible depends on the weather. First, the air has to be cold to produce a contrail to begin with, so usually trails appear behind high-flying aircraft (above 26,000 feet), such as commercial jets. Once the contrail forms, it will tend to disappear rapidly if the air is very dry, or it will linger and expand if the air is very humid. In the latter case, the contrail eventually expands into an ordinary cirrus cloud formation, like those that form naturally under the same conditions.

So you are talking about contrails, even if you think you aren’t, because there’s no such thing as chemtrails. The difference between trails that disappear and trails that linger depends only on the weather, not on the content of the trail, which is always made of plain water.

The trails are composed of water ice crystals that form as the result of the combustion of hydrocarbon-based fuel. When heat is applied to aviation or jet fuel in the presence of oxygen, a major byproduct is water (the hydrogen in the hydrocarbon + oxygen in the air when heated produces water as a byproduct). You’ll see the same thing down here on earth in the winter. Notice that a liquid dribbles out of the tailpipe of the car in front of you — its water. If it were cold enough and humid enough, fog would roll out of the tailpipe leaving a trail behind the car. In fact, in the Antarctic in the dead of winter when the air temperature on the ground is -60° F and the air is humid, vehicles leave a trail of ice fog as they move over the ice.

Try this nifty little app to illustrate the point:

http://itg1.meteor.wisc.edu/wxwise/contrails/t3.html

Oh, and one other thing. Most of the “chemtrail” nutters make a big deal of patterns of trails in the sky such as multiple intersecting trails that create giant “X’s” or a series of parallel lines, etc. What would you expect? Some planes fly north-south courses to get to their destination, others fly east-west courses and still others fly to a point in the sky then make a turn to adjust their course. Aircraft use radio beacons to guide their progress and often fly from one beacon to another over the course of their flight. There are standard “airways” at lower altitudes and “jetways” at high altitudes just like Interstates. It helps keep the airspace organized. The United States has the busiest air traffic at all altitudes of anywhere else on Earth.

There’s no conspiracy here, just ignorance and overactive imaginations.