What happens when you have a reservation for a car rental but there are no cars left?

We're sorry, sir, but we don't have any cars left.

That was my unpleasant welcome to Michigan by Hertz.

I had a reservation. They saw the reservation. The problem: Hertz hadn't actually saved me a car.

So here I was, just off a plane in Kalamazoo, suitcase in tow and no car. I wasn't the only one stranded and — I later learned from my cab driver — it happens somewhat regularly.

After the initial shock, all that kept flashing through my head was a 1991 Seinfeld episode where a car rental firm doesn't have Jerry's reserved car.

"But the reservation keeps the car here. That's why you have the reservation," Seinfeld says. "You know how to take the reservation, you just don't know how to hold the reservation. And that's really the most important part of the reservation: the holding."

Reserving a car is different than almost any other travel product.

That leaves the industry with many more reservations than actual renters.

So just like airlines sell more tickets on planes than seats, car rental agencies sometimes don't have enough cars to meet their demand.

"During the course of a year, this phenomenon is a rare occasion and occurs less than 1 percent of the time," Paula Rivera, a spokeswoman for Hertz Global Holdings, Inc., parent company of Hertz, Dollar and Thrifty, said via email.

If a reserved car class is not available, it is Hertz's policy to provide a complimentary upgrade to the next available car class.

In situations like mine where there are no cars left at the airport, Hertz will let customers rent from a competitor and pay the difference, or pay for a cab to and from your hotel, asking you to return the next morning when more cars might be available.

Alice Pereira, a spokeswoman for Avis Budget Group, Inc., outlined a nearly identical policy at her company. A representative for Enterprise Holdings, the parent of Alamo Rent A Car, Enterprise Rent-A-Car and National Car Rental, did not respond to numerous requests for comment.

For me, a solution wasn't so simple. Everybody else in Kalamazoo was out of cars and Hertz said it would be days until they got more vehicles.

I had an early meeting for work the next day and needed a car. Luckily, the airport in Grand Rapids, Mich. — 58 miles (93 kilometers) away — did have some cars available. An hour and $150 cab ride later, I was finally in a car.

When I returned the car three days later, Hertz took the $150 off my bill and gave me one of those $50 vouchers.

So what can you do to prevent a similar fate? Not much.

The company also lets customers in some locations reserve specific model cars, which helps make sure that you get the right size vehicle. Rates for those cars, however, are typically higher than a generic "intermediate" or "compact" rental.

It also pays to sign up for the rental firms' loyalty program, which is free.

Rivera said members of Hertz's Gold Plus Rewards program "by virtue of their loyalty, are served first." In my case, my membership didn't help — but I got the sense that nothing would have.

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