I think I saw contrails, but this day some military F-5 aircraft were passing by over the city, and I don´t know if they release a white smoke.That day I saw white lines of smoke in the sky, all linear and all crossed by others,as in the contrails photographs, and that day military F-5 fighter jets were passing all over the city, but I don´t know if they release a linear white smoke. That day was not rainy nor cloudy, it was sunny; not windy.((NUFORC Note: The Mexican Air Force may fly North American F-5 jet fighters. Any jet aircraft is capable of generating "contrails" (CONdensation TRAILS") when they fly at sufficiently high altitude.))