Standby, returning to the states, you could buy different tickets on different airlines for that day, again fully refundable within 6 month. When you book a day in advance, it will show you a face to the right of the listing ... Red, magenta, green. Some kind of indication of how full that flight is, however, that indication does not work on all the airlines. I've booked on Emirates indicating a red face, but lots of seats were available.