Thanks for your response. For example, on 12/1 travel agent books me on a 12/10 trip from EWR to ORD in first for $1190. On 12/10 I may have meeting delayed that requires me to switch to a later flight that leaves 1-2 hours later. The fare for first on that alternative flight is only $800. There are times where United would do it as an even exchange, and there are times where I would receive a future flight credit for $390.

let me know if that is the detail you are looking for or if there’s anything else I can provide. Thanks!