Navigation in the air.

I regularly drive up and down the M3 and have recently noticed that frequently there are Chinook helicopters following the motorway. The most I have seen at once is 3, which is probably all that we have left in the country at present!

Whilst I can understand that a motorway is a very easy handrail to follow to your destination it seems very strange that in these days when GPS is in such common use, these aircraft do not to fly directly to their destination.

So what is going on? It may be that they are learning natural navigation techniques instead of reliance on electronics, but what ever is happening I hope they are not going to rely of following motorways when they get out to Afganistan or Iraq.

Does anyone know why they do this?