[strela]

I don't know for sure why the cloud hung around as long as it did. Low high-level wind speed just seemed a logical reason to me. Somebody like Physicist could probably tell you for sure why it happened.

[AdA$tra]

AP Wire: The two unarmed re-entry vehicles were expected to travel 4,200 miles in 30 minutes and strike targets in the Marshall Islands, the Air Force said in a statement.

Yikes!

[Physicist]

The wind speed in important--certainly I often see jet contrails last longer than 10 minutes if the conditions are right--but it also seems likely that this missle trail is very much larger and farther away than the ones you see from jets, so it will seem to move and disperse more slowly.