Just because you show up at the airport with a ticket reservation doesn’t necessarily mean you’ll end up on your intended flight. Most airlines overbook flights to compensate for last-minute cancellations, but they don’t always get the numbers right. And with so few seats open on later flights, fewer folks are volunteering to get bumped. As a result, the number of involuntarily bumped passengers is up, having grown 45 percent between 2005 and 2009, according to the Department of Transportation.“Instead of fixing the problem,” says Tony Polito, an associate professor in the college of business at East Carolina University who has published academic articles about airline industry issues, “they are institutionalizing it.”