So you're planning for your next holiday. You know that you've got 10 days of vacation time, and you'd like to go somewhere in December, while the kids are off from school. You're not sure where you want to go, but a beach vacation to beat the winter weather sounds nice. Maybe Hawai'i, maybe the Caribbean. You run a few dates and destinations through a free aggregator such as Google Flights, Skyscanner, Hopper or Kayak, then you toggle on price alerts, and decide to pull the trigger when a deal hits your inbox.
Or... you sign up for a paid flight alerts subscription service, such as Going (formerly Scott's Cheap Flights), Dollar Flight Club, Thrifty Traveler or Next Vacay. Then you set your home airport, a few dream destinations, whether you prefer economy or business tickets, and wait to see what comes through.

If these two options sound similar, it's because they are.
Read on for my analysis of the value of the paid flight deal aggregators – and three free alternatives you might not know about.