Bebe Emerman
KIRO 7 Eyewitness News Consumer Investigator

For the last two decades, it's been a love affair at 30,000 feet. Let's face it: When it comes to perks, it's been tough to beat frequent flyer miles, with their promise of free tickets and first class upgrades.

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But, as we've discovered, this perk has got some problems, and a lot of passengers may soon find their travel dreams crashing to earth.

David Jacobson believes in good customer service. It's what he gives every day at his North Seattle espresso stand.

But he says it was not what he got from the airlines when he tried to book a recent trip to Europe for himself and his girlfriend using frequent flyer miles.

"When I went to get the tickets, it was impossible; it was just impossible," Jacobson said. "The bottom line is we ended up getting one ticket for free, using 60,000 miles, and paying for another ticket."

But that was just the beginning.

They wanted to travel from Seattle to Athens, Greece, and were hoping for direct flights and short layovers.

Instead, "we ended up flying literally from Seattle to LAX, LAX to O'Hare, O'Hare to LaGuardia, we had to transfer to LaGuardia to JFK, we had a six-hour layover," he said. "We had just enough time to rent a hotel room shower and get ready for the rest of our flight which was to Charles de Gaulle and then de Gaulle to Athens."

It was truly, he says, the trip from hell.

"It took two and a half days on the calendar to get there."

Unfortunately, though, it's a scenario that's becoming all too familiar.

For years, passengers have chosen flights, rented cars, booked hotel rooms and even picked the credit cards they used to pay for those flights, cars and rooms -- largely because of mileage rewards they received.

As a result, passengers in the U.S. are now sitting on more than 9 trillion unused frequent flyer miles, according to Webflyer.com.

"This is a problem that is not going to get better," said Steve Danishek, a travel expert.

Danishek says for years, the airlines have raked in billions selling their miles to credit card companies and hotel chains, but now the bill is coming due.

"We have too many passengers who want to use their mileage to fill the number of seats the airlines wish to make available," Danishek said.

The result is a vicious cycle that increasingly is leaving passengers stuck in the center seat, if they can find a seat at all.

We went online, trying to use miles for flights and were quickly disappointed.

Even booking months in advance, we turned up zero flights for popular vacation destinations like Hawaii and Mexico.

Even getting to NYC this summer turned out to be virtually impossible, mileage-wise.

When we were able to find a flight, we often got dinged for 40,000 miles instead of the usual 25,000.

Experts say "Get used to it."

"They may not get the day that they want, they may not get the time of the day that they want, they may not get the airport that they want. They may have to go to a nearby airport and rent a car and drive."

And, if you're traveling with others, be prepared to split up.

When Alki resident Delaney Parshall and her fiancé visited Cancun last winter, they not only traveled on separate planes, but on separate days as well.

"He had to take an overnight flight, fly in to another city, he had an overlay of about seven hours," Parshall said. "So basically he almost lost a day and a half of vacation time, by the time I got there, I was exhausted too, so it was really a hassle."

Of course, the airlines could remove the hassle by simply making more seats available. But with planes these days chock full of paying passengers, they'd prefer not to do that. And that means a new era of frequent flyer frustration.

"This is a problem that could lead to passenger rebellion and lawsuits," said Danishek.

If you want to improve the odds of snagging a free seat, you not only need to be flexible on the date you travel, the time of day, and which airport you fly into but also on the number of miles you're willing to commit.

Those 25,000-mile trips are still out there, but they're getting tougher and tougher to find.