FYI... Was going ORD-LHR recently, wife and kids(2) in tow. Flight was 8:45PM overnight and I had upgraded all four w/miles. Checked in at 5:30 as a result of the horror stories about O'Hare check in delays. Was told at the counter they were already looking for voluntiers and they tag our bags STANDBY. (VERY important in tthe days and age of bag matching to traveller). When at gate they asked for anyone without any check on bags and no one was moving. They offered $600 ea., a departure 15 min. earlier to Frankfurt with a LH trip back to LHR, 3 hrs. later. They were offering to put folks in Bus. as well on the ORD-LHR leg. We jumped on it, faired very well and to boot had the miles for the original ORD-LHR upgrade returned. Using those & bumps for a week in Maui in early April. THANKS UA!!