Originally Posted by jsloan

Were seats available for sale? "Full" on the app is more of a suggestion than anything else. I've SDC'ed onto flights that were listed as Full, and I've also seen flights go from Full to Available repeatedly. I think it shows Full when the flight is 100% booked, but that doesn't mean they're not willing to oversell by a few seats more.

My guess is that if any volunteers from the first flight were needed, they were put into confirmed space on the second flight, even if it appeared "Full" on the app. That might have pushed the second flight into an overbooked situation, which could then have been resolved with more volunteers or natural attrition (no shows / missed connections). It's also possible that they knew they'd need two seats and proactively grabbed them (making the flight show Full in the app). And, from time to time, UA does get the number exactly right -- they overbook by exactly the number of no-shows they end up with and the flight goes out even.

I'd actually love to volunteer only to find that the seat they tried to offer wasn't really there. I'd expect a big payday.