all this talking about volcano debris causing cooling in the atmosphere and effects on weather etc, let's mention the crap they've been spraying in the jet stream for years now, apparently to aid in military radio transmission, but who knows, I can say this though, as an aerospace engineer, it's definitely not a contrail and I've seen days forecast for clear skys end up milky white by the time they're done spraying...and they constantly rotate pilots, maintenance crews etc, so they don't work with each other for extended periods of time, that, can have an effect on the weather.