Kathleen and Eugene Bianucci paid $5,770 for a pair of round-trip tickets between San Francisco and Dublin this year on Virgin Atlantic Airways. A few days before their trip, Kathleen, a fitness instructor from San Bruno, Calif., broke her leg. She had to be hospitalized for a week and her doctor grounded her for six months. When she told the airline about the accident, a representative promised her a full refund.

You can probably guess what happened next. Virgin, which had extracted the five grand from Bianucci’s credit card in just a few seconds, balked at returning the money. It asked her to fax hospitalization records, but when she sent them, it responded with a form e-mail saying that the information was “not sufficient” and asking her to send the same documents again.

“I felt as if the airline was trying to deny the refund,” she says. “They wouldn’t tell me specifically what they wanted, and everything I sent them was not sufficient, according to them.”

Before she contacted me for help, Bianucci had done everything she could to get her money back. She’d re-sent her hospital records several times and tried to contact the airline by phone. But Virgin would communicate with her only by fax or e-mail. “It’s a real nightmare,” she says.

Passengers have complained about the slow pace of airline ticket refunds ever since there have been airline tickets to complain about. Like other businesses, air carriers are reluctant to part with the revenue they collect from customers, even when they’re supposed to.

The Transportation Department, which regulates airlines operating in the United States, requires air carriers to reimburse your credit card company within seven business days after receiving a complete refund application. But the government allows some wiggle room, noting that the rule doesn’t apply to all payment methods and warning air travelers that the credit “may take a month or two to appear on your statement.”

That kind of wishy-washiness is all the license an airline needs to delay or deny a refund, passengers claim. Indeed, over the long term, the industry-wide practice of delaying refunds — of customers being sent countless form letters and having to communicate with a fax machine — is enough to make some travelers walk away from the process, essentially leaving their money on the table.

Virgin Atlantic says that in Bianucci’s case, the delay wasn’t deliberate. After I contacted the airline on her behalf, it reviewed its records and said that her refund had been on hold pending receipt of a document verifying her medical condition and subsequent hospitalization. It apologized for the delay and said that it had located one of the faxes she had sent. “All is resolved now,” said Nadia Basil, an airline spokeswoman.

What’s behind the sluggishness? There are three leading causes, and they have nothing to do with dark airline conspiracies to pocket the money for unused tickets.

The first cause is something called a ticket tariff. It spells out the specific rules governing the ticket, including the circumstances under which a fare would be refunded. Strictly speaking, every airline ticket is refundable. For example, if an airline cancels a flight, it owes you a refund whether you’re flying in first class or in the back of the plane, and whether you paid with cash or with frequent-flier miles. Ticket tariffs often are long, complex documents rendered completely in capital letters and subject to various interpretations. (It isn’t unusual to find a tariff with confusing or contradictory language.) Before issuing a refund, an agent must first determine whether the tariff allows it, which isn’t always easy.

The second cause of delays is the staffing and other resources required to handle a refund speedily. Airlines, like other businesses, have plenty of incentive to invest in technology that takes money from customers’ credit cards but fewer reasons for sinking resources into systems that quickly refund money. For example, until this summer, United Airlines had no automated system for refunding certain seat upgrades. The only way to get your money back for an Economy Plus upgrade fee would have been to ask for it. Those refunds were handled manually, one by one.

And third, as the Transportation Department suggests, even when an airline posts a refund, it can take one to two billing cycles before it shows up on a credit card statement. Although that isn’t an airline-specific problem, it can be seen as foot-dragging on an airline’s part.

I’ve had many conversations with DOT representatives over the years about the pace of refunds, and the rules haven’t always been clear. For example, the seven-day rule is only for credit card refunds, and in the past it was thought to apply only to fully refundable tickets. I asked a DOT representative whether that’s still true, and he said it isn’t. “The rule on prompt refunds would also apply to non-refundable tickets where a refund was due, such as for a significant flight delay,” says DOT spokesman Bill Mosley. A regulation that took effect in July 2011 addresses purchases made by cash and check, requiring airlines to return a customer’s money “within 20 days after receiving a complete refund request for cash and check purchases.”

But those historical gray areas might explain why passengers have waited six months or more for ticket refunds in the past. There’s no reason for an airline to move faster, and it’s breaking no rules by hanging on to customers’ money.

Airlines should refund all passengers with equal speed, says aviation consultant Michael Miller. But he suggests that air travelers take a few precautionary steps when they want a refund. These include contacting the airline quickly to ask for one and saving every e-mail to prove that you’ve complied with the carrier’s requests.

So what’s the solution? Maybe DOT’s ticket refund rules need to be more uniform, stipulating that all refunds should be issued within seven business days, regardless of the payment method, and should include fares and fees charged to a passenger for optional services that couldn’t be used because of an oversale or cancellation. And your rights to a refund should be clearly disclosed on every ticket.

If those policies had been in place, incidents such as the four-month delay in Bianucci’s refund — and all the inconvenience that went along with it — might be far less common.

Elliott is National Geographic Traveler magazine’s reader advocate. E-mail him at chris@elliott.org.