Expedia

On its app, the online travel agency Expedia offers Price Drop Protection on most flights. For a nonrefundable fee, the service will monitor the price of a flight booked through Expedia. If the price drops, the service will refund the difference.

How it works: Using the Expedia app, a flight search turns up a price-tracking screen with insights into past price fluctuations and future predictions — insights it began offering last year — along with current fares and the option to hedge against them falling. On a recent search, the lowest round-trip in late May between New York and Los Angeles came up at $219, which Expedia predicted would be the “best price we expect to see between now and takeoff.” Nevertheless, it offered Price Drop Protection at $21, meaning that if the fare fell between purchase and take off, Expedia would refund me the difference.

Cost: Fees, which are nonrefundable, vary based on the ticket price, but there’s no annual limit on refunds.

Bottom line: Expedia’s price insights offer a guide on whether buying Price Drop Protection might be worth it. In the previous example, I would be betting $21 that my fare would drop more than $21, or to below $198, which seemed unlikely.

Airline price holds

When searching for flights on the websites of a few major carriers, including American and United Airlines, consumers can opt to freeze a fare for a while.

How it works: United’s FairLock program allows users to hold a fare for a fee, which varies based on ticket price and length of the hold. Using a recent search for a round trip in May between Chicago and San Francisco, a $372 fare would cost $5.99 to hold for three days, $8.99 for a week and $12.99 for two weeks. Within the hold period, users can pay the guaranteed price for the flight or let it expire. Either way, the fee is nonrefundable.

American Airlines says it offers free 24-hour holds and extended hold options with nonrefundable fees on select flights. A recent search for a round-trip flight in May from Dallas-Fort Worth to Los Angeles turned up a $366 round-trip fare. After clicking through to the final payment page, I was offered a 24-hour complimentary hold. Despite numerous other searches, I was unable to find an extended hold offer.