Below is a practical, step-by-step guide to finding and booking award (award-ticket / mileage) flights that combine multiple airlines. It covers planning, searching, tools, tricks for harder itineraries, and booking options.

1. Decide your basics first

• Dates (or date range) and how flexible you are (± days, weeks). The more flexible, the easier.
• Airports you can realistically use (home airport + alternatives).
• Which points/currencies you have or can get (Amex, Chase, Citi, airline miles, etc.).
• Priority tradeoffs: fewest miles, lowest taxes/fees, shortest travel time, one-stop booking vs. two separate tickets.

2. Learn airline alliances and important partner relationships

• Alliances: Star Alliance, Oneworld, SkyTeam. Award space can usually be searched/issued within an alliance (e.g., United can book most Star Alliance partners).
• Non-alliance partners & transfer partners: many carriers have bilateral partnerships (e.g., Air France/KLM with Alaska; many banks have transferrable points to multiple airlines).
• Knowing which program can ticket which partner is critical — it determines whether you can issue the multi-carrier itinerary as one award or must book segments separately.

3. Map the itinerary in pieces (routing plan)

• Sketch your preferred routing: outbound (city A → B → C) and return. Include acceptable alternate airports and routing variations.
• Break complex routes into segments you can search individually (A→B, B→C, etc.), then check if those segments can be combined under one program.

4. Search strategy — start with alliance/transfer program that gives the best value

• If you know which program you want to use (e.g., you have lots of Alaska miles), start by searching that program’s award search tool for partner availability.
• If you don’t, search availability across several alliance hubs:
  • Star Alliance: search on United, Aeroplan, or ANA (ANA may have fuel surcharges).
  • Oneworld: search on British Airways, Qantas, or American AAdvantage (availability varies).
  • SkyTeam: search on Delta (Delta’s partner award search is limited) or Air France/KLM (Flying Blue).
• Use the program that can both find and issue the combination — otherwise you’ll have to stitch segments or transfer points.

5. Use tools that aggregate partner award space

• Multi-carrier award search/aggregation tools (paid and free) — they save time:
  • AwardWallet / Point.Me (formerly JuicyMiles / AwardFares) / ExpertFlyer / ITA Matrix for routing ideas (not award inventory) — some are paid.
  • Airline search engines and alliance websites often show partner space. Example approaches:
    • Use United/Aeroplan for Star Alliance partners.
    • Use Alaska for many U.S. & some international partners.
    • Use British Airways or Iberia to find Avios-eligible flights (good for short-hauls).
• Note: Many aggregator tools require subscriptions for advanced features.

6. Search segment-by-segment to assemble multi-airline itineraries

• If the alliance program or search engine can’t show a full multi-carrier itinerary, find award space on each segment and then:
  • Try to recreate the itinerary in the program that will issue the ticket (search by segment there).
  • If the issuing program can see all partner segments, you can book in one award.
  • If not, you’ll likely need to book segments separately and accept separate tickets (risk: no interline protection if delays break connections).

7. Watch for and manage taxes, fees, and fuel surcharges

• Some carriers impose high fuel surcharges (e.g., some European carriers historically). Programs differ in how much tax and carrier-imposed surcharges you pay.
• Sometimes using a different issuing program (or routing through a different country) greatly reduces taxes/fees.

8. Use flexibility tools and calendars

• Flexible date calendars (±3 days / monthly view) are invaluable. Most airline award search pages and many tools offer calendars showing the cheapest award dates.
• Start with flexible-date searches to find pockets of availability, then tighten to exact days.

9. Consider mixed-cabin and positioning flights

• Mixed-cabin itineraries (economy + business) can be significantly cheaper in miles. Decide if mixed-cabin is acceptable.
• Positioning flights: sometimes it’s cheaper/more available to book a paid or low-miles flight to a major hub to catch the long-haul award from there.

10. Use phone agents and expert help when needed

• If online booking fails but award space exists on segments, call the airline program that will issue the ticket — agents can often ticket complex partner itineraries that the website cannot.
• If you’re uncomfortable or the routing is very complex, paid services (award booking services) can assemble and ticket itineraries for a fee.

11. Consider transfer timing and point transfers

• If you need to move transferable points (Amex/Chase/Citi) to an airline partner, check transfer times — some are instant, some take days.
• When award space is rare, transfer only once you can confirm the award can be ticketed (or that holds are available). Some programs allow holds or hold+pay; others do not.

12. Protect yourself: cancellation, change, and missed-connection rules

• Know rules for cancellations/refunds and change fees for the program you’re using.
• If segments are on separate tickets, you lose protection for missed connections — budget time, or buy protected connections.

13. Practical tips and quick workflow

• Step A: Use a calendar search on 2–3 programs that can issue the award (e.g., United, Air Canada Aeroplan, and Alaska).
• Step B: For each candidate date, check availability segment-by-segment on the operating carrier’s site or on the alliance partner page to confirm.
• Step C: Try to assemble and price the itinerary on the program you plan to use. If it fails online, call that airline’s award desk.
• Step D: Only transfer points if award space is ticketable or on hold.
• Step E: After ticketing, immediately screenshot/record the reservation details, ticket numbers, and operating carrier confirmation numbers.

14. Common gotchas

• Websites do not always show all partner space — phone agents sometimes can see/book more.
• Arbitrary routing rules and fuel surcharges vary by program — two programs can price the identical flights at very different mile/fee totals.
• “Hidden city” / throwaway segments can violate carrier rules and risk account penalties — avoid.

15. Examples of when to book separately vs together

• Book together (one award) when the issuing program can ticket all carriers — you get one PNR and protection for connections.
• Book separately if partners aren’t ticketable together or if one segment uses a different award currency — but be aware of risk.

16. Resources to learn and tools to use

• Airline program award search pages (United, Aeroplan, Avios members, Alaska, AAdvantage, Flying Blue).
• Aggregator/paid tools: ExpertFlyer, Point.Me, AwardWallet, SeatSpy, and paid award services (use cautiously).
• Frequent flyer communities: FlyerTalk, Reddit /r/awardtravel for up-to-date tips and program quirks.

17. Final checklist before booking

• Confirm award space on each operating segment.
• Confirm the issuing program can ticket all segments together.
• Price the itinerary in the issuing program and confirm total miles + taxes/fees.
• If using transferrable points, confirm transfer times and only transfer when you can ticket.
• Save/print all confirmations and ticket numbers.

If you’d like, tell me:

• the cities/dates (or date range) you’re considering,
• which miles/points you have, and I can outline a concrete search/booking plan for that specific trip.