Assuming this part of the show is historically accurate: As seen in this clip from HBO's Band of Brothers Lt. Winters is boarding a aircraft en route to Omaha Beach. Winters is wearing what looks like a piece of cardboard around his neck with the number "67" on it, the same number of the aircraft he is boarding. From the looks of it the number relates to the aircraft in which he his boarding, but I'm interested to know more. Is it just to not "lose track" of which aircraft you are assigned to? Thanks in advance.
It’s to help organize the ‘chalk’ for that flight. The other soldiers would get lined up behind the chalk leader and the number helps to identify which particular flight they belonged to. This is still practiced today in the US military, where a chalk leader is given a number for his flight which is usually a patch placed on their shoulder. This means the flight crew can quickly ensure that they have the right information for their manifest. It’s simply to help keep a large movement of soldiers like this organized, especially on the scale of this example.