The gap: you can't search your own route
Jack's Flight Club is a curated-deal broadcast: you tell it a departure airport or region, and it sends whatever cheap fares it finds from there, to wherever they happen to go. What you can't do is tell it "I want to go to Tokyo" and have it search specifically for that. If the destination you actually want hasn't turned up in what it's broadcasting, you're waiting on luck, not a search.
What milo does instead
Set the exact route, flexible dates, cabin and a target price, and milo searches for that specific trip, not whatever's cheap today across every destination. If it's a real bargain to somewhere you weren't planning to go, that's what Jack's Flight Club is for. If it's a specific trip you already have in mind, that's what milo is for.
For the full feature-by-feature comparison, see Milo vs Jack's Flight Club vs Going.
Frequently asked questions
Can I search my own route with Jack's Flight Club?
No. Jack's Flight Club is a curated-deal broadcast based on your departure airport(s) or region - you can't tell it a specific destination and have it search for that route. Milo does exactly that.
Does milo replace Jack's Flight Club?
Not necessarily - they solve different problems. Jack's Flight Club is for general inspiration from wherever deals turn up. Milo is for when you already know the trip you want and need something to watch for your price.
Is milo cheaper than Jack's Flight Club?
They're not really comparable on price, since they're built for different jobs - broadcasting general deals versus tracking a specific route. See milo's pricing page for exact plan costs.