Contrails!

[Chris Knight]

unlikely with contrails, the checkerboard as you call it is explained above, airways crossing.

Oh, I don't know:

or on a larger scale from space:

[johnholmes]

I suspect, if you plot the airways maps on top of the second one it will show pretty clearly, albeit with some drift due to winds, just what I posted about airways

In the states as here the movements of military aircraft are not necessarily governed by airway routes, hence there will always be scatter over major countries with a large air force.

Edited October 24, 2007 by johnholmes

[mettalfabrik]

this might help this is upper level routing 20000ft+

courtesy of http://www.ais.org.uk/aes/login.jsp

[The PIT]

But if my lawn is anything to go by they leave something else.........

Fertilizer wow amazing aircraft.

[Gray-Wolf]

Fertilizer wow amazing aircraft.

Fertilizer hot no less!

[mettalfabrik]

check out the trails in this sat pic in the atlantic as they arrive this morning

http://saturn.unibe.ch/rsbern/noaa/dw/real...ent/n1bcurr.jpg

[Turnedoutniceagain]

Grid pattern is simply down to flightpaths - a an airliner going from Gatwick to Edinburgh will fly south-north and be intersected by one going from Amsterdam to Dublin flying east-west, for example. Given thousands of flights over the UK every day in all directions, it's little wonder a grid pattern sometimes appears.

Well said, I believe Green 1 goes from LHR to the US, via Shannon in Ireland. Amber 25 goes from Glasgow, south over Brecon & over to france.They intersect over the TACAN/VOR Beacon near Sennybridge. Airlines can't fly willy-nilly around the sky.

NATO Airforces also observe a strict one-way system around the hillier parts of the UK, ie, Usk Valley, Elan valley etc in Wales are all one-ways only.

[johnholmes]

see post 28 above for the UK airways.