Even if you gave up your childhood piggy bank years ago, it’s still helpful to remember that every penny counts. Case in point: In 2015, airline travelers passing through security lines left a whopping $765,759.15 behind in plastic bins and buckets, USA Today reports. Most of it was loose change—and all of it was collected by the TSA.

Thanks to a law passed by Congress in 2005, the money officially belongs to the TSA after local stations collect it and the agency’s financial office counts it. Still, the TSA says it does its best to return flyers’ lost possessions (including money). However, sometimes people don’t return for them.

“TSA makes every effort to reunite passengers with items left at the checkpoint, however there are instances where loose change or other items are left behind and unclaimed,” TSA reportedly said in a statement. “Receipts of unclaimed money are deposited into a Special Fund account so that the resources can be tracked easily and subsequently expended.”

Members of Congress once tried to give the leftover money to U.S. military service members and their families, as part of the TSA Loose Change Act 2013. However, the bill didn’t pass the U.S. Senate. Instead, the TSA currently uses the cash to fund security operations.

And 2015 isn’t the only year that the TSA made big bucks from spare change. In 2014, the agency collected $674,841.06 worth of unclaimed money. In 2013, they made $638,142.64. In fact, the amount has gone up every year since 2008, when only $383,413.79 was collected. In total, airline passengers have left behind more than $4.3 million in airport security lines over the past eight years.

Some airports have tried to help people donate their pocket change to good causes, USA Today points out. For instance, Denver International, Phoenix Sky Harbor International, and a few other airports all have pre-security donation boxes that benefit local non-profits.

By the end of February, the Phoenix Sky Harbor airport had collected $13,548.87 for charity since installing spare change kiosks in 2015. Meanwhile, Denver International Airport, which started its program in 2013, has accumulated $282,722.

[h/t USA Today]