Vapour trails from what aircraft?

Vapour trails in the sky yesterday morning (22 March) indicate unusual flight trajectoiries. What was/were the aircraft?


The photograph was taken at around 11h30 am on Tuesday 22 March, from near to the Mairie of Onex and looking east towards Annemasse. It would appear to show that aircraft at a reasonably high altitude circled around for a while then departed (somewhere). The vapour trails were very slowly disappearing, so it could not have hapened too long before the photo was taken. The trails are not obviously from Geneva airport traffic, nor are they on the normal arrival or departure routes.

Today the airport Web site reveals that tonight, and for the next three nights, aircraft from neighbouring aerodromes will be circling around doing thermal imaging of all of Geneva canton. Such imaging has already been done in 2009 for the communes of Meyrin and Vernier. The aircraft concerned will be a fixed-wing aircraft operating between midnight and 3am and a helicopter operating between 6am and 8h30am. Both will fly at an altitude of 600 metres (say 2000 feet) above ground.

I expect to be able to identify these aircraft fairly easily (unless, as too often happens, the helicopter is authorised to fly without an operational transponder). If they have a modern GPS-equipped transponder it will even be possible to plot their trajectories (though I consider this unlikely). It should also be interesting for people who are affected by helicopter overflights to see what a helicopter 2000 feet overhead looks and sounds like.

Which still leaves me curious about the vapour trails in the photograph!

Any ideas?



During the last twenty or so years, I've seen a couple of airliners doing one circle at high altitude above the region before continuing on their original headings. Regarding your picture I wouldn't be surprised the trails were made by fighter jets, because about two months ago I saw three of them coming from south south-east and heading north with a right turn approximately above the Jura. About one hour later the trails were as wide as the one on your picture. It happened betweeen 11 and 11:30 since I was following the AMS-CPT flight that flew by not too long after.

Posted by: Patrick | 03/23/2011

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