There was also a special formulation for the SR-71. I think it was JP-7 and it had a very high flashpoint suitable for a hot airplane.

The JP-8 fueled F-16s from UANG and Hill AFB that fly frequently over my work places (especially today, since Pres. Bush is in town) do not leave contrails, but I believe that has much more to do with the constantly low humidity in Utah than with the fuel formulation.

I've seen F-16s pulling contrails in humid conditions.

Contrails are nothing new to jet engines. During WWII, piston powered military aircraft often pulled contrails when operating at high altitudes. I've read that the allied photographic reconnaissance pilots (who flew "alone, unarmed, and unafraid") used contrails to their advantage. They'd climb until they were just below the altitude where contrails formed and cruised there for the entire mission. The allied reconnaissance planes (primarily conversions of the Spitfire, Mosquito, P-38 Lightning and the P-51 Mustang) were fast enough that an enemy plane generally needed to dive to catch them. However, when the enemy planes climbed high enough to dive, they'd be pulling contrails which gave away their position. That gave the reconnaissance pilots a little warning and a slight edge to help them survive against long odds.