That would explain it
Isn't there meant to be a minimum separation distance between 2 aircraft, both horizontally and vertically?
I know it is very hard to judge what height each of them was at, but it stayed that formation pretty much from west to east. Given they were at similar heights, those first two look awfully close don't they? Or am I just wrong and the inflight separation is in the hundreds of feet?
EDIT: Reading this;http://www.pilotfriend.com/training/flight_training/nav/airways.htm
"..in general, air traffic controllers and pilots are required to maintain a horizontal distance of 5 nautical miles between 2 aircraft flying at the same altitude."
Now if that is a general rule with only a little flexibility, and the fact they looked to be at a similar altitude (from the ground at least), they do not look to be 5 nautical miles apart (5.755 normal miles to us land lubbers).
As I said, I can't ever recall seeing 2 planes on the exact same flight path within such a short time frame, let alone 3.
(Complete guesswork by an utter simpleton, with no aviation knowledge btw)