http://en.wikipedia.org/wiki/Nellis_Air_Force_BaseConfirmed through an anonymous archeologist working on the air base.
Unconfirmed through a witness in the judicial sense.
"Las Vegas reporter Marcus Dalton writes that an archeologist working throughout Nevada began noticing 'all white unmarked aircraft' preparing for take-off at Nellis AFB, and at the Mancamp Complex near Tonopah in the late-90s.
'It was these unmarked planes that were constantly laying down the criss-crossing X patterns of lingering chemical-spray trails over Southern Nevada,' the archeologist stated. When he asked the military escort accompanying his civilian research team into 'sensitive' areas around Nellis, about the planes, he was strongly advised, 'You didn’t see anything.' [Tribune Media Group June 26/06]"
http://globalskywatch.com/chemtrails/ubbthreads.php?ubb=showflat&Number=6910#Post6910 
