Flight routes HAVE to be close to each other. The minimum horizontal serperation isn't that much. it's only a mile or two IIRC. The size of the
countrail is going to depend on the plane, and the conditions. And there are still quite a few planes that look like a KC-10 flying out there.
While vertical minimum separation has been reduced, aircraft still must stay at least 5 nautical miles away from planes at the same altitude. The
FAA’s air traffic control en route centers closely monitor all aircraft flying at high-altitudes.
Separation Regulations
From the ground, five nautical miles is NOT much.
[edit on 11/29/2005 by Zaphod58]