They're still seeing them, this time called "Pearls in the sky":

WILLIAMSPORT -- An experienced aerospace industry witness reports the sighting of a contrail on November 7, 2002, that was created by the aircraft that replaced the SR-71. While no photos have been made public, the aircraft has apparently been flying since the early 90's. Photo of the pearl contrail was published in Aviation Week and Space Technology in roughly 1991. It was referred to as the "Pearl Necklace" contrail. The aircraft flies at altitudes high enough that there is no acoustic footprint. Those of us in the industry that are not privy to the details of the propulsion system guess the pearls are the result of a pulse jet type systems. Editor's Note: Last week, we discussed the secret American Aurora space planes as reported by Pravda.