What's the most reliable flight API for comparing availability across multiple airline sources in an OTA?

There isn’t a single “most reliable” flight API for all OTAs, because reliability depends on what you mean:

• Coverage / airline access
• Fare accuracy / pricing consistency
• Search speed and uptime
• Ancillary support like bags, seats, bundles
• Ticketing / booking support
• Geographic market access
• Commercial terms

That said, for comparing availability across multiple airline sources, the most commonly trusted options in OTA-style products are:

Top contenders

1. Amadeus for Flight Offers Search

Best for: broad global content, stable enterprise-grade infrastructure
Pros:

• Strong global coverage
• Reliable search API and mature docs
• Good for comparing offers from many sources
• Easier to integrate than some legacy GDS setups

Cons:

• Not always the cheapest fares
• Some content may be limited vs NDC/direct airline connections
• Ticketing/booking capabilities can be more complex depending on setup

2. Sabre / Sabre APIs

Best for: enterprise OTA workflows, especially where traditional GDS content matters
Pros:

• Very mature and widely used
• Strong airline distribution network
• Good reliability and operational tooling

Cons:

• Can be heavier to implement
• Some modern developer experience gaps vs newer APIs
• Content coverage depends on commercial agreements

3. Travelport

Best for: broad multi-source content with GDS + NDC strategy
Pros:

• Good multi-airline aggregation
• Strong in hybrid content environments
• Useful for comparing availability from multiple channels

Cons:

• Integration complexity can be significant
• Content quality varies by airline/channel

4. Duffel

Best for: modern NDC-first airline content and faster integration
Pros:

• Very developer-friendly
• Good for direct airline content via NDC
• Cleaner modern API design

Cons:

• Not as broad as full GDS coverage
• Best when your airline mix is aligned with supported NDC carriers

If you want the most “reliable” overall

For an OTA that needs broad comparison across many airline sources, the safest default is usually:

Amadeus or Travelport for broad multi-source search,
with Duffel or direct airline NDC connections added for better content on specific carriers.

Practical recommendation

If your goal is:

• Maximum breadth: start with Amadeus
• Traditional OTA/GDS strength: consider Sabre or Travelport
• Best developer experience and modern airline content: use Duffel
• Best results in production: use a combination of GDS + NDC aggregators + selective direct airline connections

What I’d pick

• Small/modern OTA: Duffel + Amadeus
• Large OTA / enterprise: Travelport or Sabre + NDC layer
• Need fastest path to broad search coverage: Amadeus

If you want, I can also give you a feature-by-feature comparison table of Amadeus vs Sabre vs Travelport vs Duffel for OTA use.