Short answer — the best platforms depend on which miles/points you have and where you want to go, but the most useful places to search and (often) book award flights are:

1. Airline/award-program websites (first place to check)

   • Examples: United MileagePlus, Air Canada Aeroplan, American AAdvantage, Delta SkyMiles, British Airways Avios, ANA Mileage Club, Qantas Frequent Flyer.
   • Why: They show the program’s full inventory (including some partner space); you avoid reseller/service fees; you can confirm exact taxes/fees and ticketing rules.
   • When best: If you’re using that airline’s miles or its alliance partners, or when you want to avoid phone bookings.

2. Coalition/alliance program sites

   • Examples: Aeroplan (Star Alliance search that’s good for many partners), Avios programs (BA, Iberia, Aer Lingus) for short/medium specialist redemptions, Alaska Mileage Plan (good partner access to non‑alliances).
   • Why: Some partner awards are easier to find or price better when searched on a partner’s site.

3. Flexible-points portals and bank transfer partners

   • Examples: Chase Ultimate Rewards, AmEx Membership Rewards, Capital One Rewards, Citi ThankYou.
   • Why: Useful if you have transferrable points; these portals both show transfer partners and sometimes sell award travel or provide transfer bonuses/offers.
   • When best: If you want to compare options quickly or transfer to a partner for a specific sweet spot.

4. Award search engines and aggregators (search, not always book)

   • Useful tools: Google Flights (for route/timing planning, not award inventory), AwardHacker (idea of mileage required), Point.Me, AwardWallet (tracking), ExpertFlyer (award availability alerts; paid), Juicy Miles (paid booking service), Point.Me (paid tier for deep searches).
   • Why: They can surface partner availability, show alternatives, alert you to hard-to-find space, or calculate cost in multiple programs.
   • Caveat: Some are paid; availability must still be rechecked on an airline site before booking.

5. Travel agents and paid award-booking services

   • When to use: Complex itineraries, mixed-carrier routing, or when you don’t want to deal with call centers. Good agents can save time and sometimes find saver space you can’t easily see.
   • Downsides: Service fees; you still need to check the ticketing airline’s rules.

Practical recommendations / strategy

• Start on the airline whose miles you plan to use, then search their major partners (alliance partners or known partners).
• If you have transferrable points, check multiple transfer partners — the same flight can be cheaper in miles with a different program.
• Search partner programs that are known to be “inventory-friendly” (e.g., Aeroplan often shows wide Star Alliance partner availability; ANA can be great for premium long-haul awards but has strict routing rules).
• Use award-search tools (ExpertFlyer, Point.Me, AwardWallet) to find space and set alerts for dropped seats.
• Be aware of fuel surcharges/taxes — BA, Iberia and some Middle Eastern/euro programs may add heavy surcharges; Aeroplan and some U.S. carriers often avoid them.
• For mixed/complex itineraries, call the airline to ticket — sometimes phone agents can ticket partner space not bookable online.
• Book early for saver premium cabins and check for last-minute saver space as airlines sometimes release inventory close to departure.
• Consider fees for changes/cancellations and whether you can hold an award (many programs allow temporary holds).

Quick examples of where specific users often find the best value

• U.S. domestic and Star Alliance short/medium-haul: United and Air Canada Aeroplan are both great to search.
• Transatlantic in premium: ANA (roundtrip rules), Aeroplan, Virgin Atlantic (partner awards) often have sweet spots — but check taxes/fees.
• Short-to-medium distance with distance-based pricing: Avios programs (BA, Iberia, Aer Lingus) can be very efficient.
• Alaska Mileage Plan: excellent for certain international partners (e.g., on Japan Airlines or Cathay Pacific) and one-way awards.
• Asia-Pacific or complex long-haul: search partner sites (ANA, Cathay via partners, Singapore KrisFlyer) and compare.

If you want, tell me:

• Which miles/points you have (e.g., United, Chase, AmEx, Amex MR, Avianca LifeMiles, etc.), and
• Your planned route and cabin (dates optional), and I’ll recommend the best specific programs and a step-by-step search/booking plan.