Thanks for posting this photo, Ivy. I've only seen a few snow geese on the ground, so analyzing the picture was a good way to learn a few field marks.
Black primary feathers are common to snow geese and whooping cranes, along with a generally white body. Whooping cranes are considerably longer with a wingspan reaching over seven feet. A longer, pointy bill and long black legs that extend beyond the tail in flight account for some of the extra length. Whooping cranes have a longer, thinner neck.
Snow geese are fairly common during migration. Were these flying northward, possibly, and were there more than five in the group?
The middle goose of the top three is of particular interest--it seems to have a dark collar extending over the breast that can't be explained by a difference in lighting. The underwings appear darker, as well. I am wondering if this might be a blue morph ("blue goose") or an "intermediate" (Peterson guide).
They were flying south with a large group of Sandhills and there was a group of about 5, this one dark one was colored that way, I havent ever seen Whoopers or Snow Geese and I knew Whoopers had black wing tips. They say the place where I go does have Whooping Cranes land, (must be rare) so I need to go more often to watch for them, although I really doubt I will ever see them. I recorded their sounds too, it was awsome!