Contrails or 'Chemtrails' - what is going on in our skies?

It is 8AM and the skies over Adelaide are covered in chemtrails…..

This post appeared on Facebook. It seems thousands of people, possibly millions, now believe that aircraft are deliberately spraying them with chemicals on a daily basis. For people involved with aviation it seems so ludicrous that no rebuttal is necessary.

So what is really going on?

Hardcore conspiracy theorists will always believe that anyone who doesn't validate their position is part of the conspiracy. There's no entry point into that world view. However there are a great many people who see vast plumes criss crossing our skies and have started to wonder if perhaps there isn't something behind all of those insistent posts on Facebook. This article is intended for them.

From what I can tell the chemtrails conspiracy theory has its roots in the 90's when the US Air Force conducted some contingency planning surrounding the hypothetical weaponisation of weather. Being a progressive organisation with a war fighting charter, they regularly conduct all sorts of hypothetical scenarios. Recently there was mainstream news coverage of one such hypothetical which modelled an alien invasion. Conspiracy theorists had fun with it, but there was no actual invasion. A scenario like this tests the organisation's ability to respond to unknown threats and technologies. In short these hypotheticals keep them 'sharp'.

Added to this is the work that has been done on 'geo-engineering'. There's no shortage of scientists who argue that we could help mitigate the effects of global warming, by creating artificial cloud barriers. Once again hypothesising about something doesn't make it a reality and in order to have any chance of working it would need to cover vast areas, let alone the theorists who suggest it would make matters worse. Another variant of the chemtrails idea is that the population is being sprayed with chemicals for various reasons.

Most people understand that clouds are masses of condensation created by the temperature differences that occur with different altitudes and air pressures. When aircraft move through the air they essentially create streams of 'cloud' – condensation trails, usually abbreviated to 'contrails'. Their formation is most often triggered by the water vapor in the exhaust of aircraft engines.

They can however also be created by changes in air pressure across other areas of the wing surface. As a wing generates lift a vortex if formed at each wingtip, and sometimes at wing flaps. Reductions in pressure and temperature can cause condensation, which in turn can also become visible, especially at landing and takeoff. Aircraft have always done this and depending on the conditions these contrails may be more or less noticeable, and may hang around or disperse.

What has changed markedly in recent years is the power of jet engines and the sheer quantity of aircraft in the skies. The former creates far more pronounced contrails whilst the latter means you will see a lot more of them.

A key element to the chemtrails conspiracy theory is that someone must be getting a lot of aircraft up in the sky to do all this 'spraying' and that these aircraft must be suitably equipped for the job. Putting aside which organisation may be fiendish and cashed up enough to do this for a moment, the reality is that what happens in the skies is tightly controlled, especially over urban areas where there is a lot of activity.

Air Traffic Controllers monitor every aircraft, and there is a virtual army of engineers, maintainers and various other personnel that are constantly going over every aircraft. So if they are operating in normal airspace, every single one of those people need to be in on the conspiracy.

Beyond that however is the vast legion of 'plane spotters' who document every aircraft and every movement. You can never underestimate these people and they have been known to break major aviation stories. Every aircraft and every air movement attracts their attention. If there was even a single aircraft whose schedule and purpose was not well documented you can be sure that these types would be onto it. So far there hasn't been a single 'Edward Snowden'. Not one former Air Traffic Controller or other aviation experienced person has come forward with verifiable evidence. If something this horrendous was going on you'd expect someone would have a pang of conscience, or be sufficiently disgruntled to blow the whistle, and provide documentary evidence. What the Snowden episode has shown is how very hard it is to keep anything secret these days. All it takes is a memory stick sent to Wikileaks.