Over the past 16 hours or so, I have been searching repeatedly. There is a flight combination that comes up, basically two options for RDU-MSP, then DL 40 MSP-LHR, then three options on AF LHR-CDG.

I've done this search (RDU-CDG) maybe 60 times or so, mostly just hitting the "find flights" button, and these flights appear and disappear constantly.

Considering that there are two options for RDU-MSP and three for LHR-CDG, the linchpin must be DL40. Is it really possible that availability on this flight yo-yo's every 5 minutes? That either DL is changing availability, or that someone starts to book the last seat, then changes their mind?

I understand that in my frustration I may be preaching to the choir, but anything I can learn here will help me understand how to actually use the website - if using the website is actually possible.