If it was an airliner, it would be on an IFR flight plan, and tracked by radar. The authorities could easily identify the flight path and knowing the location of the camera could verify the photo as being from a known flight. If they did all this, why wouldn't they state more detail to support their statement? Especially when the first photo posted above by "amacbean" looks a lot like the photos taken of the mystery contrail. I don't know what the real answer is, but our "authorities" don't look so smart to me.
Tom is absolutely right. "It was an airliner contrail" does not cut it. We need to know which airliner, at what altitude, on what course, etc, etc, plus some detailed analysis of how that specific airliner could have created that specific contrail. All that should have taken about a half hour to figure out, but it didn't - in fact we still don't have that.
No matter what this thing was, this whole episode has been a complete and utter fiasco for the military, the FAA and even the media. Are there any grownups left in positions of authority anymore?