For education and discussion only. Not for commercial use. An unusually long contrail running east to west across the horizon this morning had some people concerned, but officials said it was a normal aircraft phenomenon. "Contrails spread out like this many times," said Eric Schminke, a National Weather Service meteorologist in Wichita. What happens, he said, is that as some planes cruise in altitudes of 35,000 to 38,000 feet high, particularly in colder weather, their contrails can be pushed along and spread out by the jet stream, which can sometimes average 110 to 125 knots. "That happens a lot," Schminke...