Big mystery: what changed in the mid-to-late 90s? The airliners were flying at significantly higher altitudes due to advanced engines and aerodynamics. Though the absolute humidity was lower (fewer kilograms/meter^3 of water vapor), the relative humidity was higher (carrying capacity of the air was near saturation), so the contrails would persist longer.
But long-lasting contrails stretching across the sky were commonplace in the 1950s where B-52s were operating at 50,000 feet altitude. I saw them as a pre-school child.
Big mystery: what changed in the mid-to-late 90s? The airliners were flying at significantly higher altitudes due to advanced engines and aerodynamics. Though the absolute humidity was lower (fewer kilograms/meter^3 of water vapor), the relative humidity was higher (carrying capacity of the air was near saturation), so the contrails would persist longer.
But long-lasting contrails stretching across the sky were commonplace in the 1950s where B-52s were operating at 50,000 feet altitude. I saw them as a pre-school child.