Looking for the Best Deal on Airfares? Consider a Price Freeze.

To buy or to wait? Given the wild fluctuations of airfare prices, that is a frugal flier’s persistent dilemma. A fare found today may tick up tomorrow, double next week or fall.

Now Google and other online travel platforms aim to take the uncertainty out of the equation by offering guarantees or freezes, often on fares they predict won’t shrink.

Sitting on mountains of data, these platforms say they have a good grasp on predicting price fluctuations. On fares where guarantees are offered, “our algorithms are confident that the price is unlikely to drop between booking and departure,” said Jade Kessler, a product manager for Google Flights, which recently launched its Price Guarantee pilot program. “Our goal really is to help travelers avoid that feeling of buyer’s remorse and help them to know that no matter what happens after they book, they’re getting the best deal possible.”

Like Google Flights, Kayak already allows travel shoppers to track flights for insights on pricing trends and recommendations on when to book. Though not necessarily available on every flight, guarantee and price-hold programs go a step further, and often cover hotel and car rental reservations, too.

But how do they work, and are they worthwhile? To find out, we analyzed the leading programs in price freezes and guarantees that don’t require a membership to access.

Google Flights

This month, Google Flights announced a pilot Price Guarantee program that will monitor an eligible flight from purchase to take off and refund the difference between the airfare paid and the lowest fare found in that period, as long as it is more than $5.

How it works: Travelers must book their tickets on Google Flights, which, unlike online travel agencies, acts like a pass-through sales portal so that fliers can still accrue loyalty points and hear directly from an airline about schedule changes. Eligible flights must originate in the United States. To date, there are relatively few that qualify. The platform is primarily working with Alaska, Hawaiian and Spirit.

Searching popular routes on those airlines on Google Flights, I recently found a $144 round-trip in May between Chicago and Las Vegas operated by Spirit that had the Price Guarantee badge. I had the option to Book on Google to get the Price Guarantee at the same price as booking on Spirit. Google’s price analysis showed the fare was $90 cheaper than usual, so I did not expect it to fall.

Google Flights then monitors the price…