Everyone has seen them: High in the blue sky, a pencil-thin plume slowly draws a white line. If you have good eyesight, you can just make out the plane that heads it, and if there is not too much noise around you, you can hear the distant roar of engines. For as long as man has built and flown high-altitude airplanes, this sight has existed. In the recent decades as even the high skies become congested with traffic, it is a common sight, and on some days the sky is virtually criss-crossed with contrails.

What are contrails?

When air cools, its ability to contain water vapor is reduced, quite drastically. This is the reason for clouds, mists and fog: As air cools, some of the invisible water vapor condenses into tiny droplets that hang in the air and scatter the light, giving a whitish look. On a cold day, you can see your own breath: The warm, moist air you exhale cools and the water vapor condenses and becomes mist. An engine "exhales" water vapor too; fuel is a compound of carbon and hydrogen, and when it burns, it is turned into carbon dioxide and water. Normally, the water vapor in engine exhaust stays invisible because it is quite hot and it disperses in the surrounding air before it cools off sufficiently to condense, but under certain conditions of (low) temperature and humidity, it will condense into a white mist.

Such conditions become more and more frequent with increasing altitude. At 10km (30,000ft) where jet-liners fly, conditions for condensation are the norm: On most days, a plane traveling at that altitude will form a contrail. Sometimes, the mist disperses quickly, the tiny droplets forming it evaporate back into the surrounding air and the mist disappears a short way from the plane. All we see is a small white "comet" that moves across the sky. On other days, the droplets freeze into ice particles and stay visible for a long time: We see a persistent contrail that forms a long line in the wake of the plane and may sometimes hang around long after the plane left, drifting with the wind, sometimes spreading. On such days, if one of the trafficked air corridors is overhead, the sky may get zebra-striped with contrails. In special conditions, when the high air is super-saturated with moisture, we may see a single contrail trigger wide-spread condensation forming a continuous layer of high clouds or mist covering parts of, or the entire sky.

There is a second kind of contrails. You may have seen photos or movies of jet fighters performing some abrupt maneuver. Small contrails come from wing-tips and other places. When air is compressed, it gets hotter, and when it is decompressed, it gets colder. An aircraft, even when flying straight and level, creates a complex of pressure-waves that cause local temperature displacements. Under the right conditions, this gives rise to contrails. Since no moisture is added to the atmosphere, such contrails are less dense and have much shorter duration that the ones coming from the engine exhaust. Under conditions where pressure-wave contrails are created, exhaust contrails will be very prominent, and we rarely notice the other type.

An awesome sight

I have often thought that people who did not know about aircraft, if such exist, might find the contrail phenomenon an awesome, fright-inducing sight. However, the fright seems not to be limited to people ignorant of aircraft. A whole movement has sprung up who have developed a sinister conspiracy theory around contrails. Of course proliferating on the internet.

Enter chemtrails

These people have named them chemtrails and they claim that the evil government (who else? Only surprise is that aliens seem not involved this time) have decided to poison the population. The reasons why the government should want to do this are a bit vague, but it is claimed that it is done by letting high-flying planes spread chemicals over the countryside, in a sort of grand crop-duster operation. The evidence for this? Well, haven’t you seen all those planes drawing a trail over the sky?

This has to be one of the more whacky ideas around, but thanks to the internet, it can be spread around quite a lot, so let us dissect it, bit by bit.

Government wants to poison people

Well, understandably, the chemtrail people tend to get a bit vague here. Any government, democratic or not, good or evil, thrives on its population. It may want to be loved by the people or be feared by the people, it may want to tax the people, suppress the people, exploit the people, but it is very difficult to imagine what reason a government would have to kill the people. History confirms this. Even governments that appeared to be headed by evil madmen, like Hitler, Stalin, Pol Pot, or Saddam Hussein, have not attempted to destroy their population at large. They may have tried to exterminate certain demographic groups, but only minorities.

To make the idea even more silly, those pesky contrails show up over any country, not just one. So it would seem that practically all governments in the world have been able to reach an agreement on this scheme. Of course, we know how great the probability is that all governments would agree on ANYTHING.

Would it work?

Now, let’s assume for a moment that the government does want to poison the population. Perhaps they do not want to kill them, just pacify them, or some other chaotic evil intent. Would having high-flying aircraft spread chemicals over the countryside be a useful tool for this? Well, not exactly! At altitudes of 30,000 ft, some severe conditions exist, among other things winds of over 200mph. So, before those chemicals can drift to the ground, they may have been blown hundreds of miles away! Not exactly useful if you want even the slightest control of where you spray or how much.

But it gets worse: Just think of the logistics. To regularly spray an area like the USA, and the chemtrail people claim it happens most every day, you would need hundreds of planes in constant operation. Specially built or modified planes. Each plane requiring pilots, ground-crew, maintenance crew. Thousands of tons of fuel and chemicals would have to be purchased and distributed.

Think of the risks: Any government or government department caught red-handed in such an operation would be crucified, riots would ensue, political opponents would be handed landslide victories on a silver platter. And how could it be kept secret? In a country like the United States, a president has had to resign after fiddling a bit with papers at the head-quarters of the opposing party; only a handful people knew about it, but it got out, and hell broke loose. Another president had a little fun with a female intern in his office; only three people knew about it, but it got out and… you know the rest. The chemtrail operation would involve thousands of people, many of which would have to know exactly what went on, others would have an excellent chance to put two and two together. People whose friends and families would be among the victims. How long would you guess it would take for it to leak? …Well, how long does it take to make a phone-call?

And it is not only the people directly involved who could blow the whistle! Flight controllers and radar operators all over the countries would see these mystical aircraft and begin to ask awkward questions. An air traffic control tracks EVERY plane in its area.


- Basic idea of chemtrails is highly unlikely: No government would undertake such a project.

- The project is impossible: If a government wanted to poison people, this would not be a feasible method.

- The thesis in unnecessary: The explanation for the observations is simple and straight-forward.

In other words, chemtrails are fiction, and not very good fiction at that.

Threats from contrails

So, contrails are harmless? Not quite. Apart from being the visible clue to some rather massive pollution, they are actually man-made clouds. It has long been speculated whether the massive concentration of contrails over some areas had an effect on the climate. On September 11th, 2001 a unique and tragic opportunity arose to test this. For several days after the terrorist attack, all regular planes over the United States were grounded, the only flights venturing into that vast airspace being absolutely essential military flights. So for three days that September, practically no contrails were generated.

Later, meteorological data were analyzed, and it was shown that temperatures were actually different in areas where the sky is normally full of contrails. The nights were a little colder and the days were a little warmer. The differences were only a degree or two, and the average temperature over 24 hours did not change measurably. Does this mean anything? We don’t really know, but we now know that contrails do influence the climate in the more congested areas.




Below are a number of putative frequently asked questions. Nobody sent me those questions, but after perusing several websites of chemtrail believers, I find that these are some questions they might ask:

Chemtrails are often made side-by side, as if one or several planes have carefully flown a pattern to cover the entire sky. Why would commercial airliners do that?

Well, that will happen if they follow parallel courses for some reason, but mostly this phenomenon has a different reason: For safety reasons, air traffic is kept in corridors. The sky is actually full of one-way motorways. So the planes all follow identical courses, like beads on a continent-wide string. However, as mentioned in the article high winds prevail in those high altitudes, and the and the lane phenomenon is mostly due to cross-wind: The first plane makes a contrail, which drifts with the wind. Those winds are easily 100mph, so by the time the next plane comes along, the contrail from the first has drifted a considerable way to the side. As a long succession of planes fly the highway, each adds a new lane to the drifting pattern, till the sky is virtually striped. To verify this, watch a contrail while keeping reference to a ground-object (tree, mast, or tall building). You will see it drifting.

Why is the sky sometimes covered by a checkerboard pattern?

Same reason as above, only you are watching one of the many places where corridors cross. They are not intersecting, because there is a difference in altitude, but that is not evident from the ground.

Sometimes I see trails that go on and off so the resultant stripe is dashed. Surely planes do not turn their engines on and off like that?

No they don’t. But the boundary between the altitude where contrails form and where they don’t can be quite sharp, and not only can this boundary be at different height at different times, but there are very often a sort of waves in the air. If you have ever seen one of these time-compression movies of clouds, that wave motion can be very evident. When there is no clouds, we don’t see it, but it can still be there, and when a plane happens to fly right through these waves, you can see its contrail go on and off.

Sometimes chemtrails look like they are dripping?

Contrails are a form of clouds, and they can take on strange shapes. In the wake of an airplane is a trail of quite violent turbulence. To generate lift, the wings have to push down on the air as they pass; this is a complex mechanism, but the bottom line is that to keep 70 tons of airliner airborne, you inevitably create a long wake of turbulence. Depending on conditions, this turbulent trail may twirl the contrail into quite exotic shapes.

I once saw a picture of long stripes of quite thick and low-hanging clouds. Surely those are not contrails?

No, they are a natural phenomenon, although some of the mechanisms are the same. Especially on summer days, you will see these little cauliflower-shaped cumulus clouds. Often the sky is clear in the morning, then these little clouds begin to form, and by afternoon, it is semi-overcast. They are generated when the ground is heated by the sun. This makes the air rise over hot surfaces like cities, rocky surfaces, or open fields. When the warm, moist surface air reaches a certain altitude (depending on conditions this will happen between 500 yards and two miles up), it has expanded and cooled so much that the moisture condensates, and a cloud forms. If it is a calm day, it will more or less sit there and maybe grow big and strong, ending as a thundershower. If there is a fair to strong wind, however, the cloud drifts away from the area that started it. However, the condensation process releases heat, so once started, the cloud is self-sufficient: As it drifts along, it sucks up more moist air and can even grow this way. But the area that caused it to form will generate a new cloud, which will drift away, and after some time, we have long rows of clouds drifting across the sky. If the conditions are just right, they can form long, contiguous cloud stripes.

I often see an extra high amount of chemtrails appearing just before a weather change, so I think they are doing something in order to influence the weather?

In fact it is the other way around: The change in weather influences the contrails. When the air becomes more moist at high altitudes, contrails are more likely to form and will persist longer. Ahead of an approaching front, especially a cold-front, the low-lying layers of air are pushed upwards. Rising air expands (because the pressure decreases) and expanding air gets colder, thus putting the moisture in it closer to the condensation limit, and more contrails form. The amount of planes is the same, but if they don’t form contrails, you are rarely going to notice a high-flying plane.

Sometimes, the day starts out clear, then chemtrails are made, and into the afternoon, the sky gets totally hazed over.

As the sun heats the air, moist air rises. Sometimes it will form clouds, on other days it just generally pushes the whole column of air upwards, and come the afternoon a high-altitude haze forms. This is a normal weather-mechanism, and it is for this reason that sunsets are usually redder than sunrises. Except for the rare occasion of super-saturated air, contrails have nothing to do with it, except that they of course add to the hazy look of the sky.

After days with lots of chemtrails, both I and others feel slick, coughing and having flu-like symptoms.

Well, contrails are most prominent on moist, hazy days. So is air-pollution. The hazy, possibly polluted air may make you cough and feel uncomfortable, but the culprit is the cars and chimneys right around you, not the planes passing miles over you. Watching the sky and imagining evil people spraying you isn’t going to make you feel any better.

I have seen some photos where the trail starts right at the wings of the plane, even if the engines are rear-mounted. Surely those cannot be created by the exhaust?

No, those are created by the pressure-waves that exist around the wings. Those pressure-waves are basically what keeps the plane up, and in the right conditions, they can be seen, although they will mostly be difficult to see against the much more prominent contrail from the exhaust.

I have seen photos of organic fibers and something that looked like blood-cells, collected on days with many chemtrails. Do you suggest that these reports are fake?

No, I have seen those micro-photos, and they seem genuine enough, but I find it extremely unlikely that they should come from high-flying planes. Just think about it: How fast do such near-microscopic particles fall? A few ft. per minute? Those planes fly at 30,000ft or even more. Microscopic particles and fine aerosols fall at maybe 2 ft. per minute or less, that means they would take about ten days to reach the ground from 30,000ft. And, of course, by that time they might have been carried a thousand miles from the release point. No, whatever is in those pictures is simply pollution, and if you want to find the source, you should not look up, but upwind.