letsfg 2026.5.79

Flight search & booking for AI agents. 200+ airline connectors run locally, free. Direct booking URLs via letsfg.co concierge or Developer API.

LetsFG — Your AI agent just learned to book flights.

200+ airline connectors. Real prices. One function call. Search 400+ airlines at raw airline prices — $20–$50 cheaper than Booking.com, Kayak, and other OTAs.

Three ways to use LetsFG

	Local (this SDK)	PFS (Programmatic Flight Search via letsfg.co)	Developer API
Search cost	Free	Free (Twitter/X token, one-time setup)	Prepaid credits
Booking URL	1% concierge fee (min $3) via letsfg.co	1% concierge fee (min $3) via letsfg.co	Direct airline URL, no fee
Speed	20–40 s (fast mode) · 1–15 min (full)	60–90 s	2–5 s (discover) · 60–90 s (full)
Setup	pip install letsfg	Twitter/X challenge → letsfg.co/for-agents	letsfg.co/developers

Want direct airline URLs without any per-booking fee? Use the Developer API — prepaid credits, results in seconds, no checkout step.

Install

pip install letsfg

Search flights immediately — no account, no API key:

letsfg search-local LHR BCN 2026-06-15

That fires 200+ airline connectors on your machine. Search is free. Booking links are delivered via the letsfg.co concierge flow (1% fee, min $3) — see Unlocking offer results below.

# Search using only Brazilian sites
letsfg search BSB SDU 2026-05-24 --country BR
# Or by region
letsfg search GRU LIM 2026-06-15 --region latin-america

Short on time? Use --mode fast to search only OTAs + key airlines (~25 connectors, 20-40s instead of 6+ min):

letsfg search-local LHR BCN 2026-06-15 --mode fast

Authentication

from letsfg import LetsFG

# Register (one-time, no auth needed)
creds = LetsFG.register("my-agent", "[e-mail]")
print(creds["api_key"])  # "trav_xxxxx..." — save this

# Option A: Pass API key directly
bt = LetsFG(api_key="trav_...")

# Option B: Set LETSFG_API_KEY env var, then:
bt = LetsFG()

# Setup payment (required before unlock) — two options:

# Option 1: Stripe test token (for development)
bt.setup_payment(token="tok_visa")

# Option 2: Stripe PaymentMethod ID (from Stripe.js or Elements)
bt.setup_payment(payment_method_id="pm_1234567890")

The API accepts only Stripe-generated tokens or payment_method_id values — raw card numbers are not accepted.

The API key is sent as X-API-Key header on every request. The SDK handles this automatically.

Verify Your Credentials

# Check that auth + payment are working
profile = bt.me()
print(f"Agent: {profile['agent_name']}")
print(f"Payment: {profile.get('payment_status', 'not set up')}")
print(f"Searches: {profile.get('search_count', 0)}")

Auth Failure Recovery

from letsfg import LetsFG, AuthenticationError

try:
    bt = LetsFG(api_key="trav_...")
    flights = bt.search("LHR", "JFK", "2026-04-15")
except AuthenticationError:
    # Key invalid or expired — re-register to get a new one
    creds = LetsFG.register("my-agent", "[e-mail]")
    bt = LetsFG(api_key=creds["api_key"])
    bt.setup_payment(token="tok_visa")  # Re-attach payment on new key
    flights = bt.search("LHR", "JFK", "2026-04-15")

Quick Start (Python)

from letsfg import LetsFG

bt = LetsFG(api_key="trav_...")

# Search flights — FREE
flights = bt.search("GDN", "BER", "2026-03-03")
print(f"{flights.total_results} offers, cheapest: {flights.cheapest.summary()}")

# Unlock booking link (1% fee, min $3, charged via letsfg.co)
unlock = bt.unlock(flights.cheapest.id)
print(f"Confirmed price: {unlock.confirmed_currency} {unlock.confirmed_price}")

# Book — ticket price charged via Stripe (zero markup)
booking = bt.book(
    offer_id=flights.cheapest.id,
    passengers=[{
        "id": flights.passenger_ids[0],
        "given_name": "John",
        "family_name": "Doe",
        "born_on": "1990-01-15",
        "gender": "m",
        "title": "mr",
        "email": "[e-mail]",
    }],
    contact_email="[e-mail]"
)
print(f"PNR: {booking.booking_reference}")

Multi-Passenger Search

# 2 adults + 1 child, round-trip, premium economy
flights = bt.search(
    "LHR", "JFK", "2026-06-01",
    return_date="2026-06-15",
    adults=2,
    children=1,
    cabin_class="W",  # W=premium, M=economy, C=business, F=first
    sort="price",
)

# passenger_ids will be ["pas_0", "pas_1", "pas_2"]
print(f"Passenger IDs: {flights.passenger_ids}")

# Book with details for EACH passenger
booking = bt.book(
    offer_id=unlocked.offer_id,
    passengers=[
        {"id": "pas_0", "given_name": "John", "family_name": "Doe", "born_on": "1990-01-15", "gender": "m", "title": "mr"},
        {"id": "pas_1", "given_name": "Jane", "family_name": "Doe", "born_on": "1992-03-20", "gender": "f", "title": "ms"},
        {"id": "pas_2", "given_name": "Tom", "family_name": "Doe", "born_on": "2018-05-10", "gender": "m", "title": "mr"},
    ],
    contact_email="[e-mail]",
)

Resolve Locations

Always resolve city names to IATA codes before searching:

locations = bt.resolve_location("New York")
# [{"iata_code": "JFK", "name": "John F. Kennedy", "type": "airport", "city": "New York"}, ...]

# Use in search
flights = bt.search(locations[0]["iata_code"], "LAX", "2026-04-15")

Working with Search Results

flights = bt.search("LON", "BCN", "2026-04-01", return_date="2026-04-08", limit=50)

# Iterate all offers
for offer in flights.offers:
    print(f"{offer.owner_airline}: {offer.currency} {offer.price}")
    print(f"  Route: {offer.outbound.route_str}")
    print(f"  Duration: {offer.outbound.total_duration_seconds // 3600}h")
    print(f"  Stops: {offer.outbound.stopovers}")
    print(f"  Refundable: {offer.conditions.get('refund_before_departure', 'unknown')}")
    print(f"  Changeable: {offer.conditions.get('change_before_departure', 'unknown')}")

# Filter: direct flights only
direct = [o for o in flights.offers if o.outbound.stopovers == 0]

# Filter: specific airline
ba = [o for o in flights.offers if "British Airways" in o.airlines]

# Filter: refundable only
refundable = [o for o in flights.offers if o.conditions.get("refund_before_departure") == "allowed"]

# Sort by duration
by_duration = sorted(flights.offers, key=lambda o: o.outbound.total_duration_seconds)

# Cheapest offer
print(f"Best: {flights.cheapest.price} {flights.cheapest.currency}")

Error Handling

from letsfg import (
    LetsFG, LetsFGError,
    AuthenticationError, PaymentRequiredError, OfferExpiredError,
)

bt = LetsFG(api_key="trav_...")

# Handle invalid locations
try:
    flights = bt.search("INVALID", "JFK", "2026-04-15")
except LetsFGError as e:
    if e.status_code == 422:
        # Resolve the location first
        locations = bt.resolve_location("London")
        flights = bt.search(locations[0]["iata_code"], "JFK", "2026-04-15")

# Handle payment and expiry
try:
    unlocked = bt.unlock(offer_id)
except PaymentRequiredError:
    print("Run bt.setup_payment() first")
except OfferExpiredError:
    print("Offer expired — search again for fresh results")

# Handle booking failures
try:
    booking = bt.book(offer_id=unlocked.offer_id, passengers=[...], contact_email="...")
except OfferExpiredError:
    print("30-minute window expired — search and unlock again")
except AuthenticationError:
    print("Invalid API key")
except LetsFGError as e:
    print(f"API error ({e.status_code}): {e.message}")

Exception	HTTP Code	Cause
AuthenticationError	401	Missing or invalid API key
PaymentRequiredError	402	No payment method (call setup_payment())
OfferExpiredError	410	Offer no longer available
LetsFGError	any	Base class for all API errors

Timeout and Retry Pattern

Airline APIs can be slow (2–15s for search). Use retry with backoff for production:

import time
from letsfg import LetsFG, LetsFGError

bt = LetsFG()

def search_with_retry(origin, dest, date, max_retries=3):
    """Retry with exponential backoff on rate limit or timeout."""
    for attempt in range(max_retries):
        try:
            return bt.search(origin, dest, date)
        except LetsFGError as e:
            if "429" in str(e) or "rate limit" in str(e).lower():
                wait = 2 ** attempt  # 1s, 2s, 4s
                print(f"Rate limited, waiting {wait}s...")
                time.sleep(wait)
            elif "timeout" in str(e).lower() or "504" in str(e):
                print(f"Timeout, retrying ({attempt + 1}/{max_retries})...")
                time.sleep(1)
            else:
                raise
    raise LetsFGError("Max retries exceeded")

Rate Limits

Endpoint	Rate Limit	Typical Latency
Search	No hard limit (billing is the natural governor)	60–90 s
Resolve location	120 req/min	< 1 s
Unlock	20 req/min	2–5 s
Book	10 req/min	3–10 s

Minimizing Unlock Costs

Searching is free and unlimited. Unlock via the Developer API is also free; via the local/website path the concierge fee (1% of ticket price, min $3) applies once per offer. Strategy:

# Search multiple dates (free) — compare before unlocking
dates = ["2026-04-01", "2026-04-02", "2026-04-03"]
best = None
for date in dates:
    result = bt.search("LON", "BCN", date)
    if result.offers and (best is None or result.cheapest.price < best[1].price):
        best = (date, result.cheapest)

# Unlock only the winner (1% fee, min $3)
if best:
    unlocked = bt.unlock(best[1].id)
    # Book within 30 minutes (ticket price only)
    booking = bt.book(offer_id=unlocked.offer_id, passengers=[...], contact_email="...")

Local Search (No API Key)

Note: Local search results return masked booking links by default. Each offer includes offer_ref and payment_token fields. To get a direct airline booking URL, you have two options: use the concierge unlock flow (1% fee, min $3 — no API key needed) or sign up for the Developer API at letsfg.co/developers for fee-free direct links.

The SDK includes 200 connectors for airlines that run directly on your machine. No API key, no backend, completely free:

from letsfg.local import search_local

# Fires all relevant airline connectors — Ryanair, Wizz Air, EasyJet, etc.
result = await search_local("GDN", "BCN", "2026-06-15")
print(f"{result['total_results']} offers from local connectors")

# Limit browser concurrency for constrained environments
result = await search_local("GDN", "BCN", "2026-06-15", max_browsers=4)

The full search (bt.search()) runs both local connectors and cloud providers simultaneously and merges results.

Unlocking offer results

Local search results include offer_ref and payment_token on each offer. Use these to get the direct airline booking URL via the concierge flow (no API key required):

import httpx
import time

# 1. Pick an offer from local search results
offer = result["offers"][0]
offer_id      = offer["id"]
offer_ref     = offer["offer_ref"]
payment_token = offer["payment_token"]
price         = offer["price"]        # ticket price as string, e.g. "312.50"
currency      = offer["currency"]     # e.g. "USD"

# 2. Initiate checkout — returns a Stripe checkout URL
# Fee = max(price × 1%, $3.00). No API key needed.
resp = httpx.post(
    "https://letsfg.co/api/developers/checkout",
    json={
        "offer_id":      offer_id,
        "offer_ref":     offer_ref,
        "payment_token": payment_token,
        "currency":      currency,
        "price":         price,
    },
)
resp.raise_for_status()
checkout = resp.json()
checkout_url = checkout["checkout_url"]

# 3. Present the checkout URL to the user (or open it in a browser)
print(f"Pay here: {checkout_url}")

# 4. Poll until payment is confirmed
booking_url = None
while not booking_url:
    time.sleep(3)
    verify = httpx.get(
        "https://letsfg.co/api/developers/payment-verify",
        params={"token": payment_token},
    )
    data = verify.json()
    if data.get("verified"):
        booking_url = data["booking_url"]

# 5. booking_url is the direct airline link — no further fees
print(f"Book here: {booking_url}")

To skip the per-booking fee entirely, use the Developer API — it returns direct airline booking URLs on every search result.

Quick Start (CLI)

export LETSFG_API_KEY=trav_...

# Search (1 adult, one-way, economy — defaults)
letsfg search GDN BER 2026-03-03 --sort price

# Multi-passenger round trip
letsfg search LON BCN 2026-04-01 --return 2026-04-08 --adults 2 --children 1 --cabin M

# Business class, direct flights only
letsfg search JFK LHR 2026-05-01 --adults 3 --cabin C --max-stops 0

# Machine-readable output (for agents)
letsfg search LON BCN 2026-04-01 --json

# Unlock
letsfg unlock off_xxx

# Book
letsfg book off_xxx \
  --passenger '{"id":"pas_xxx","given_name":"John","family_name":"Doe","born_on":"1990-01-15","gender":"m","title":"mr","email":"[e-mail]"}' \
  --email [e-mail]

# Resolve location
letsfg locations "Berlin"

Search Flags

Flag	Short	Default	Description
--return	-r	(one-way)	Return date YYYY-MM-DD
--adults	-a	1	Adults (1–9)
--children		0	Children 2–11 years
--cabin	-c	(any)	M economy, W premium, C business, F first
--max-stops	-s	2	Max stopovers (0–4)
--currency		EUR	Currency code
--limit	-l	20	Max results (1–100)
--sort		price	price or duration
--json	-j		Raw JSON output

All CLI Commands

Command	Description	Cost
search	Search flights between any two airports	FREE
locations	Resolve city name to IATA codes	FREE
unlock	Unlock offer (confirms price, reserves 30min)	FREE
book	Book flight (creates real airline PNR)	Ticket price
search-local	Search 200 local airline connectors	FREE
system-info	Show system resources & concurrency tier	FREE
register	Register new agent, get API key	FREE
setup-payment	Attach payment card (payment token)	FREE
me	Show agent profile and usage stats	FREE

Every command supports --json for machine-readable output.

Environment Variables

Variable	Description
LETSFG_API_KEY	Your agent API key
LETSFG_BASE_URL	API URL (default: https://letsfg.co/developers)
LETSFG_MAX_BROWSERS	Max concurrent browser instances (1–32). Auto-detected from RAM if not set.

Performance Tuning

LetsFG auto-detects your system's available RAM and scales browser concurrency:

Available RAM	Tier	Max Browsers
< 2 GB	Minimal	2
2–4 GB	Low	3
4–8 GB	Moderate	5
8–16 GB	Standard	8
16–32 GB	High	12
32+ GB	Maximum	16

from letsfg import get_system_profile, configure_max_browsers

# Check system resources and recommended concurrency
profile = get_system_profile()
print(f"RAM: {profile['ram_available_gb']:.1f} GB available")
print(f"Tier: {profile['tier']} → {profile['recommended_max_browsers']} browsers")

# Override auto-detection
configure_max_browsers(4)  # clamps to 1–32

# Via CLI
letsfg system-info
letsfg system-info --json  # machine-readable

# Override via env var
export LETSFG_MAX_BROWSERS=4
letsfg search-local LHR BCN 2026-04-15

# Override via CLI flag
letsfg search-local LHR BCN 2026-04-15 --max-browsers 4

Priority: env var > explicit config/flag > auto-detect.

How It Works

1. Search — Free. 200+ connectors fire on your machine and return real-time offers.
2. Unlock booking URL — Pay the concierge fee (1% of ticket price, min $3) via letsfg.co to receive the direct airline booking link. Or use the Developer API (prepaid credits) for fee-free direct links.
3. Book — Open the direct airline URL and complete the booking on the airline's own site.

Prices are cheaper because we connect directly to airlines — no OTA markup.

---

Also Available As

• MCP Server: npx letsfg-mcp — npm
• JS/TS SDK: npm install letsfg — npm
• Try without installing: letsfg.co — search instantly in your browser
• GitHub: LetsFG/LetsFG

⭐ Star the repo — we appreciate the support.

License

MIT