I am looking for a way to allow users to add node reference to each product or whole cart @ checkout. I am making web site where users can buy items and then receive them on board flight. Products are fixed, but user needs to tell for which flight he is buying items. Flights are nodes and users has flagged these nodes so there is no problem making View with users flagged flight nodes. How would I associate one of these nodes with purchase? Nodereference from CCK would be cool, but checkout is probably not node.

Any suggestions for approach?