Not a subscription but I'd pay $100 after booking of a vacation travel planner that could give me options tailored to what I want, on flexible dates.
For ex if I want to travel to some place warm sometime in say January - March, with some flexibility on length, I end up spending a lot of time figuring out if flying a week later of some random date is way cheaper, or if the airport waiting times or fly times are terrible. If you add hotel options and flexibility in destination itself, it's a huge search space but I'd be happy with just the flight solution.
For ex if I want to travel to some place warm sometime in say January - March, with some flexibility on length, I end up spending a lot of time figuring out if flying a week later of some random date is way cheaper, or if the airport waiting times or fly times are terrible. If you add hotel options and flexibility in destination itself, it's a huge search space but I'd be happy with just the flight solution.