# Phase 0 — fare inventory research

Research date: October 12, 2026 (America/New_York). Completed before application implementation. Official provider pages are the evidence; product marketing coverage counts are provider claims, not our measurements. No live credentials were supplied. Latencies below are documented behavior or explicitly labeled engineering budgets, never measured production performance.

## Decision and honest ceiling

Start with Duffel for the most accessible broad GDS/NDC/LCC supply. Investigate AirGateway as the second commercially accessible NDC connection; certification and an agency agreement are still required. Skyscanner is the most attractive eventual comparison/deeplink connection, but its published entry bar makes it unsuitable as a promised day-one source for this new account. Implement only documented contracts, keep unavailable sources visibly unavailable, and never substitute cached trend data for live quotes.

There is no evidence for a numerical improvement such as “10% cheaper.” An uncredentialed installation finds **zero live fares**. Duffel alone gives no inventory advantage over Duffel. Additional independent supply can expose different airline offers or agency markups, and airport/date expansion can find cheaper travel, but neither proves superiority to Kayak on identical constraints. A union containing the same successful Duffel response cannot have a higher minimum before extra fees; that is a software invariant, not a measured market victory. Baggage, connection protection, currency, fees and itinerary constraints must match.

## Ranked source assessment

Rank reflects practical value for this new independent build, balancing onboarding with complementary inventory. “Contract” means permission is conditional on a signed provider agreement; public documentation is not permission to republish fares. Undisclosed commercial prices are not guessed.

| Rank / source | Access and cost | Coverage and price potential | Latency / limits | Terms and selection |
|---|---|---|---|---|
| 1. Duffel | Self-service test account; activate organization for live use. Public pricing: $3/order, 1% Managed Content, $2/paid ancillary; $0.005/search above 1,500 searches per booking. FX can add 2%. | Claims 300+ airlines across NDC, GDS and LCC. Managed accreditation helps new sellers. Already multi-channel, so another NDC API may overlap heavily. | Offer request supplier timeout 2–60 seconds, default 20s. Rate-limit headers govern; documentation illustrates 60 requests/60s, not a universal guaranteed quota. | **Initial integration.** Contract required; a search-only comparison business must confirm its agreement and economics. Raw offers do not inherently contain a consumer booking URL. Links is a separate hosted shopping/booking session. [Pricing](https://duffel.com/pricing), [content](https://duffel.com/flights), [activation](https://duffel.com/guides/getting-started), [API](https://duffel.com/docs/api/v2/offer-requests), [limits](https://duffel.com/docs/api/overview/response-handling), [Links](https://duffel.com/docs/guides/duffel-links), [agreement](https://duffel.com/services-agreement). |
| 2. AirGateway | API sales/onboarding and sandbox; certification to live. Published API price €100/month plus €1/issued booking (some airlines waived). Page also lists €2,500 implementation despite a general “no setup” headline: get a written quote. | 35+ major NDC airlines, negotiated/private fares with appropriate entitlements; may overlap Duffel. | No verified public per-account quota or production latency SLA; negotiate. Sandbox uses airline test environments. | **Second-source candidate, gated by certification.** No claim of automatic savings or universal click-out booking. [Pricing](https://airgateway.com/pricing/?type=agw-api), [environments](https://support.airgateway.com/en-US/kb/article/4/introduction-to-airgateway-platform-api), [schema](https://api.airgateway.net/v1.2/swagger-ui/). |
| 3. Mystifly / consolidator feeds | Sales-led SSP/API contract, commercial and settlement terms quoted privately; no verified public minimum or tariff. | Multi-source air distribution and private/consolidated inventory can complement public fares, particularly international markets. Entitlement matters more than adapter count. | Ask for search-to-book limits, timeout and SLA during procurement; no measured claim. | Procurement target after accounts exist; do not fabricate an adapter from marketing. [Official platform](https://mystifly.com/). |
| 4. Skyscanner Travel API | Commercial selection; official page says at least 100K monthly active users and a developed product/business plan. Pricing/affiliate revenue share negotiated. | Airline and OTA comparison with genuine booking deeplinks; strong complementary agency pricing. | Asynchronous create/poll. Create initially returns an incomplete cached subset; poll and price refresh needed for strict freshness. Limits assigned to partner. | **Conditional integration path, not available to a new account by default.** No indicative API for fare rows. [Access](https://www.partners.skyscanner.net/contact/travel-api), [live workflow](https://developers.skyscanner.net/docs/flights-live-prices/overview). |
| 5. KAYAK Affiliate Network | Partner application, sandbox/developer portal exists; negotiated production access and commercial terms, no universal free public credential. | Broad airline/OTA comparison; potentially close to the target inventory, but not inherently cheaper than Kayak itself. | No verified public universal latency/quota; contract-specific. | Corrects the brief: **a current partner flight API exists**. The old unrestricted/public model must not be confused with approved partner access. [Network](https://affiliates.kayak.com/), [developer portal](https://developers.kayak.com/), [official overview](https://www.kayak.com/c/help/about/what-is-kayaks-affiliate-program.61892.faq). |
| 6. Travelport | Trial/pre-production via sales/provisioning; production contract and implementation approval. No public universal cost/free-production tariff. | GDS and NDC offers; broader seller relationships may expose private fares. | Trial available; quota/SLA by agreement. Trial data is not consumer live inventory. | Worth negotiating at volume; cannot promise independent self-service production. [Getting started](https://developer.travelport.com/docs/getting-started), [DevKits](https://developer.travelport.com/resources/using-the-devkits). |
| 7. Sabre | Developer resources and certification environment; production credentials via account manager, agency/PCC/commercial onboarding. Fees quoted. | Broad GDS and NDC shopping; no guarantee of unique low rates versus another distributor. | Contract-specific transaction quotas and latency. | Enterprise procurement, not zero-contract supply. [Developer hub](https://developer.sabre.com/), [credential requirements](https://developer.sabre.com/guide/rest-apis-token-credentials/rest-apis-token-credentials). |
| 8. Amadeus Enterprise | Sales-led enterprise agreements; costs, quotas and certification scope negotiated. | Broad distribution under enterprise entitlements. | Contract-specific. | Viable enterprise option, not the formerly simple independent onboarding route. [Portal](https://developers.amadeus.com/toolbox). |
| 9. Travelfusion | Commercial integration, test credentials, contractual redistribution rights; no verified public implementation/minimum spend quote. | Claims 360+ low-cost/scheduled airlines, direct-connect and NDC content. Potential LCC complement. | Contract-specific; no measured latency. | Useful paid expansion after unit economics and booking support are agreed. [Official resources](https://corporate.travelfusion.com/resources), [test portal](https://xmltest.travelfusion.com/), [terms](https://www.travelfusion.com/terms). |
| 10. Expedia Rapid Flights | Partner onboarding and negotiated commercial access. | **Flights API now documented**, with shopping, price-confirmation, booking and servicing. Not merely a lodging API. | Recheck selected offers through flight details; no public universal quota/SLA verified. | Candidate after approval; do not invent an EPS free-flight key or assumed commission. [Official flight API](https://developers.expediagroup.com/rapid/flights), [partner product](https://innovation.expediagroup.com/en-us/solutions/build-your-travel-experience/rapid-api). |
| 11. Direct airline NDC | Airline-by-airline agency/technology approval, commercial and settlement agreements, certification; often IATA/ARC or an accredited intermediary. | Continuous pricing, NDC-only fare families and avoided distribution surcharges can beat legacy EDIFACT in specific cases. Duffel may already carry these offers. | Different airline timeouts, quotas and servicing capabilities; no universal number. | Select only after measuring missing coverage. BA requires valid IATA for its dashboard; LH OpenAPI registration is currently on hold (not identical to its commercial NDC program); AA recommends direct integration for agencies with IT resources. [BA](https://ndc.ba.com/start/ndc-registrations), [LH](https://developer.lufthansa.com/), [LH pricing matrix](https://lhgroupairlines.com/fileadmin/ndc-assets/03_NDC_Smart-offer/Desktop/NDC_Model_Table_OnePager_Apr2025_EN_Final.pdf), [AA](https://www.exploreamerican.com/globalsales/ndc-overview/). |
| 12. Aviasales / Travelpayouts | Affiliate registration plus separate live search API approval. Commercial usage rules and negotiated access must be confirmed. | OTA/metasearch supply; the freely accessible Data API is cached trends, not a live shopping substitute. | Search sessions/polling; limits depend on access. | Defer until approval and current search contract are supplied. [Official API project](https://github.com/travelpayouts/flights-api-project), [API docs](https://travelpayouts.github.io/slate/). |
| 13. Kiwi Tequila | **Invitation-only new partnerships** since its May 2024 announcement. Existing approved accounts can continue. No current general free signup entitlement. | Virtual interlining and LCC combinations; compare self-transfer risk and baggage as well as fare. | Contract-dependent. | Not a credible new-account dependency. [Kiwi announcement](https://media.kiwi.com/articles-and-interviews/better-for-business-kiwi-com-takes-a-new-approach-to-partnerships/). |
| 14. ATPCO / fare filings | Commercial data licensing and sales engagement, no verified independent free live shopping tier. | Filed fares/rules and retail content are inputs to pricing; alone they do not establish available seats, taxes, an offer or booking entitlement. | Feed/API freshness is different from live seat confirmation. | Excluded from live fare inventory; do not construct prices by combining filings with guesses. [Official API catalog](https://www.atpco.net/sites/atpco-public/files/2019-10/ATPCO-API-Catalog.pdf). |
| 15. Tripadvisor | Content/partner API access with terms; pricing by content product. | Public developer offering centers on reviews/location/airline content, not documented general live fare shopping. | Not applicable to live fare search. | Excluded as a fare provider. [Terra](https://docs.terra.tripadvisor.com/docs/overview), [airline content](https://developer-tripadvisor.com/partner/json-api/airline-partners/). |
| 16. Amadeus Self-Service (retired) | Official portal says decommissioned July 17; Amadeus newsroom confirms July 2026. Historical free quotas and €0.025/search articles are **not current signup offers**. | Historical exclusions included AA, Delta, BA and LCCs; archived docs are not proof of today's access. | Former test/production limits irrelevant to new onboarding. | **Excluded.** Do not build around a retired self-service signup path. [Official notice](https://developers.amadeus.com/toolbox), [Amadeus confirmation](https://amadeus.com/de/newsroom/pressemitteilung/amadeus-didi-enterprise-china), [historical FAQ](https://amadeus4dev.github.io/developer-guides/faq/). |

## Scraping and provenance

Browser-visible prices are technically extractable but unstable: session tokens, dynamic results, bot challenges, localization, personalization, IP throttling and changing markup all affect reliability. Proxy or CAPTCHA services do not grant redistribution rights. Google prohibits automated access contrary to machine-readable restrictions; other sites' specific contractual restrictions need written permission. There is no scraper, CAPTCHA bypass, proxy rotation or undocumented Google Flights endpoint in this build. [Google terms](https://policies.google.com/terms/embedded?hl=en-GB). See the research addendum for KAYAK/OTA terms and consolidator detail.

## What Kayak has that a new builder does not

Its public materials establish a large airline/OTA metasearch network and partner APIs. They do **not** establish that a new builder can reproduce every GDS, NDC, ATPCO or Booking Holdings private supply contract in the brief. Ownership is not evidence that private wholesale entitlements are shared across every brand. Treat the exact supplier stack and negotiated economics as undisclosed unless specifically documented.

The practical ceiling is approvals, commercial redistribution permission, ticketing support, search costs and private-fare entitlements. More adapters alone do not remove it. Airport/date expansion is valuable search coverage, but must be compared using the same expanded parameters in the Duffel baseline.

## Measurement protocol

Run production providers with the same cabin, adults, child ages, currencies, dates, airport combinations, stop/duration limits and departure windows. Preserve source offer IDs, request IDs, fetched-at/valid-until and response fingerprints. Compare the qualifying union against its contemporaneous Duffel subset, and separately report a fresh Duffel-only run with timing caveats. No historical calibration number counts as a current quote. Record absent/failed providers as incomplete, never a passed multi-source test. No price improvement percentage is currently established.