A few tankers were flying test missions at Boeing Field last year when I spent a little time down there.  The sun was out but heat haze was not too bad, so it was a good time to shoot.  The dark paint of the KC-46 Pegasus is not ideal for shooting on a bright day (or a dark one for that matter) but you aren’t passing it up.  What was more fun was having them taxi close by and getting a good look at the jets.  They might still have a bunch of issues to resolve but there are now plenty in service, so they aren’t a rarity.  Hopefully they will get the issues fixed soon enough.