fli

Why it's ranked here

Fli is compelling when detailed flight search must fit into code or an assistant workflow. Direct protocol access avoids browser automation, while validation, throttling, retries, and broad filters make it more than a thin request wrapper. The verdict stays mixed because the protocol is reverse-engineered, machine-readable command output remains experimental, and vendor fares may be unavailable without a browser-created session token.

What's good

The search model covers practical constraints that simpler fare tools omit: airline exclusions, alliance rules, layover bounds, cabin classes, departure windows, and locale settings. Flexible-date search supports fare discovery across a window. Python and TypeScript share models, filter encoding, and response decoding. The clients add rate limiting, exponential retry behavior, validation, and typed failures. MCP supports local standard input and streamable HTTP transports.

Tradeoffs

Direct access still depends on a reverse-engineered Google Flights protocol, so avoiding HTML changes does not remove upstream dependency risk. Vendor booking options often return empty without a browser-created session token. Command-line JSON is explicitly experimental, making it a weak contract for durable automation. TypeScript airport fields mirror the wire format with triple nesting, and Node usage requires a TypeScript loader. Booking lookup reruns searches, so filters must match.

How to use it well

Use Fli for developer tools, fare exploration, travel assistants, and scripts that need structured filtering without browser automation. Search broadly for flights or cheap dates, then request booking options for a chosen itinerary while preserving the original filters. Treat Google Flights deep links as the reliable handoff when vendor fares are absent. It does not replace the final airline or agency booking flow, nor guarantee direct vendor prices.

Observed

License

MIT

Primary implementation

Python package requiring Python 3.10 or newer

Additional language surface

TypeScript and JavaScript port published as fli-js

Installation

Python package installs as flights through pip or pipx; TypeScript package installs through bun, npm, or pnpm

Interfaces

Python library, TypeScript library, command-line interface, and MCP over standard input or streamable HTTP

Packaging

Hatchling builds the Python wheel; MCP dependencies are an optional package extra

Search coverage

One-way, round-trip, multi-city, and flexible-date flight searches