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.

Airfare is typically non-refundable once you purchase a ticket. But there's typically no penalty for reserving a car and never picking it up.

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.

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. The company will also provide a $50 voucher for a future rental.

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. Luckily, the airport in Grand Rapids, Mich. - 58 miles 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.