Two Free Roundtrip Tickets
Almost every flight I'm on from Des Moines, IA to anywhere is either overbooked or over the allowed weight limit. As a result, the airlines are always offering a free ticket or credit if someone will volunteer to take a later flight. I've never done this in the past because I'm generally on some kind of schedule. On my way back to Seattle on Saturday, I had plenty of free time. My flight schedule already included a 6-hour layover in Memphis, TN, so when the ticket counter in Des Moines was looking for volunteers I said, 'sure.' The result was a re-booking on flight with better routing (no going East to get West) and an arrival time 4 hours earlier than my original itinerary, along with a free roundtrip ticket.
Four hours later my new flight time arrived with an announcement that volunteers were needed to keep the plane under weight. Three people volunteered immediately and boarding commenced. After everyone was on the plane, one of the Northwest ticket agents came on board and said he needed 3 more volunteers or the plane couldn't leave Des Moines. Two people volunteered and I followed, with assurance that I could still be home to Seattle that night. Things got a little hairy, with the airline sweating over whether they could really deliver on their promise to put us at our destinations on time, but as luck would have it, my Minneapolis connection was delayed by 90 minutes, so I made the next flight from Des Moines to Minneapolis and still waited around for the flight to Seattle. And of course, this second re-routing is where free roundtrip ticket number 2 came into play.
While I wouldn't do this every time I travel, having a flexible schedule certain paid off this time.