Liffy is on the money. Most (all?) DC-4 tankers had the extra "eyebrow" window, presumably to assist with lining up the next run in a tight turn. I'm aware that this was a requirement in aerial survey aircraft so I imagine it's the same with tankers.
It's interesting to note that Boeing have deleted the eyebrow windows from late build 737s.
As for "Ice Pilots" I'm hoping that Nat Geo will release it on DVD after it has finished screening. There is currently no mention of it on their website.
Can anyone explain why Buffalo's C-46 C-fAVO has a lower case "f" in the registration?
Rgds