Ballast tanks inside Boeings new Dreamliner aircraft. Just full of water to simulate full pax load.
It's for monitoring data sets and also transferring the ballast around to be able to test different CG (Center of Gravity) ranges. I've always been one to doubt chemtrails due to my aviation background and all, at least for commercial aircraft. If it's being done (which I'm not 100% doubting) it's with military aircraft.
We've had plenty of breaks from Q. Some longer then others. Q will return, didn't start those other threads just for those 2 posts. :)