United Airlines Flight Search

Purpose

Given an origin airport, destination airport, depart date (and optionally a return date), trip type (one-way or round-trip), and a passenger count, return the list of available United Airlines flights for those parameters — each flight's departure / arrival times, duration, stop count, flight number(s), cabin class, fare brand, and price. Read-only — never click "Select", "Continue", or any seat / fare / book button. Stop at the results page (/en/us/fsr/choose-flights).

When to Use

• "What are the cheapest non-stops SFO → JFK on July 15?"
• "Compare one-way vs round-trip pricing on LAX → ORD next Friday."
• Daily price-watch across a fixed origin/destination/date.
• Any flow that needs UA's published fares + schedules without committing to a booking.
• Do not use this skill for award-mile / MileagePlus searches — those live on a different surface (/ual/en/us/flight-search/book-a-flight/results) and have a different fare model.

Workflow

The United flight-search UI is a JavaScript SPA. The cleanest path is to navigate directly to the search-results deep-link URL (/en/us/fsr/choose-flights?f=...&t=...&d=...&r=...&tt=...) instead of filling the homepage's typeahead form — this skips airport autocomplete, date-picker, and trip-type radio entirely, and avoids the typeahead-timing bugs that the form path is prone to. The page is still client-side rendered, so a real browser session is required to harvest the flight cards; the URL is just a shortcut into the right page state.

A residential-proxy real browser is mandatory — the site is fronted by Akamai and a bare datacenter IP gets cookie / _abck challenges before any results render.

1. Residential-proxy session config

Every browserless_agent call must carry a top-level proxy: { "proxy": "residential", "proxyCountry": "us" } argument. Confirmed by response evidence: _abck and bm_* Akamai cookies are set on every response, and a bare-IP request gets a challenge page in place of the SPA shell.

There is no session-create / release step. A browserless_agent session persists across separate calls, keyed by the call's proxy config — repeat the same proxy arg on every call to reconnect to the same warmed browser (cookies and _abck clearance intact); dropping or changing it lands you in a different, challenge-walled session. Batching the full goto → wait → snapshot flow into ONE call's commands array is the convenient default — it saves round-trips and avoids accidentally dropping the session config.

A residential-proxy real browser clears Akamai's _abck challenge automatically. If a challenge / "verify you are a human" page still persists after the page renders, it is terminal for that session — abandon it and start a fresh browserless_agent call (a new ephemeral session).

2. Construct the deep-link URL

https://www.united.com/en/us/fsr/choose-flights
  ?f={ORIGIN_IATA}
  &t={DEST_IATA}
  &d={DEPART_YYYY-MM-DD}
  &r={RETURN_YYYY-MM-DD}          # omit for one-way
  &tt={1|0|2}                      # 1=round-trip, 0=one-way, 2=multi-city
  &sc=7                            # search-class — keep 7 for cash fares
  &px={PASSENGER_COUNT}            # integer, 1–9
  &taxng=1                         # show all-in (taxes included) pricing
  &clm=7                           # cabin: 7=Economy, 6=Premium Economy, 4=Business, 3=First
  &st=bestmatches                  # bestmatches | priceasc | departtime | arrivetime | duration
  &newDateOverride=true            # use new date logic — safer on cross-month dates

Examples (both validated as 200 OK via a residential-proxy goto against the production host):

# Round-trip SFO → JFK, depart 2026-07-15, return 2026-07-22, 1 adult, Economy
https://www.united.com/en/us/fsr/choose-flights?f=SFO&t=JFK&d=2026-07-15&r=2026-07-22&tt=1&sc=7&px=1&taxng=1&clm=7&st=bestmatches

# One-way SFO → JFK, depart 2026-07-15, 1 adult, Economy
https://www.united.com/en/us/fsr/choose-flights?f=SFO&t=JFK&d=2026-07-15&tt=0&sc=7&px=1&taxng=1&clm=7&st=bestmatches

The URL accepts the airport as IATA code only (SFO, JFK, LAX, ORD, EWR, LHR, ...). City names, station IDs, or anything else gets coerced to a "no flights" state. If the caller hands you a city name, resolve it to an IATA code first (United's airport-lookup API at /api/airports/lookup/search returns 404 — not a usable surface — so resolve client-side from a static IATA table).

3. Open the URL and wait for cards to render

Run the goto → wait → snapshot as one browserless_agent call (proxy repeated):

{
  "proxy": { "proxy": "residential", "proxyCountry": "us" },
  "commands": [
    {
      "method": "goto",
      "params": { "url": "<URL>", "waitUntil": "load", "timeout": 45000 }
    },
    { "method": "waitForTimeout", "params": { "time": 4000 } },
    { "method": "snapshot" }
  ]
}

Use waitUntil: "load" — never networkidle (it hangs on this SPA). The first paint of the results grid is client-side, so the load event alone is not sufficient; flight cards aren't in the DOM until the searchFsr XHR resolves. Empirically 3–4 seconds (the waitForTimeout) covers the long tail. If the snapshot returns 0 flight-card refs, issue a fresh call with an extra waitForTimeout of 2000 before the snapshot and retry once before declaring failure.

4. Branch on what the snapshot shows

5. Extract flight cards

Each card on the results grid exposes:

• Depart time — first time string in the card (08:30, in the rendered local airport time).
• Arrive time — second time string.
• Duration — explicit text like 5h 35m (or 5h 35m +1d for next-day arrivals).
• Stop count — text like Nonstop, 1 stop, 2 stops. Parse to an integer.
• Flight numbers — text like UA 232 (or UA 232, UA 7411 on multi-leg). Capture the full list.
• Cabin / fare options — typically Basic Economy / Economy / Premium Plus / Business / First, with one price each. Capture the lowest-cabin price unless the caller specified a higher cabin via clm.
• Price — USD number, sometimes shown as $348.20* (the * indicates a Saver/award-mix fare — strip when emitting clean numbers, surface as flags: ["saver"]).

For round-trip, the page renders outbound cards first; after the user selects an outbound, return cards render on a follow-up screen. To stay read-only, extract only the outbound cards and emit them as results. If the caller wants return-leg pricing too, run a second one-way search with f / t swapped and d=<return date>.

Form-fill fallback (only if the deep-link URL stops working)

If United changes the FSR URL schema and the deep-link returns the homepage redirect or a date-picker overlay on every load, fall back to driving the homepage form — keep the whole sequence inside one browserless_agent commands array (proxy still required):

1. { "method": "goto", "params": { "url": "https://www.united.com/", "waitUntil": "load", "timeout": 45000 } }
2. Wait for the "Book travel" widget to mount: { "method": "waitForTimeout", "params": { "time": 3000 } }.
3. Click the trip-type radio ({ "method": "click" }): One-way or Round-trip (default is Round-trip).
4. Click the From field, type the IATA code (SFO) with { "method": "type", "params": { "selector": "...", "text": "SFO" } }, wait 2000ms for the typeahead dropdown, then click the first option matching the code. type does NOT auto-submit (unlike a fill-and-Enter), so the field stays open long enough for the typeahead to surface — the click → type → waitForTimeout 2000 → click <suggestion> sequence works cleanly. (An input helper that auto-presses Enter would submit the field before the typeahead surfaces — avoid it.)
5. Repeat step 4 for the To field.
6. Click the Depart date field; the date-picker overlay opens. Navigate to the target month with the > button, click the target day. For round-trip, the picker stays open; navigate + click the return day. Confirm with the picker's Done / Apply button.
7. (Optional) Update passenger count + cabin via the Travelers / Cabin dropdown.
8. Click Find flights. Page navigates to /en/us/fsr/choose-flights?... with the params URL-encoded. From here continue with the waitForTimeout → snapshot of the deep-link path (step 3).

Form-fill is ~3× slower than the deep-link path and adds two failure modes (typeahead-race, date-picker-month-overshoot), so use only when the deep-link is confirmed broken.

Site-Specific Gotchas

• READ-ONLY. Never click Select, Continue, Book, Add to cart, or a fare-option price button — any of these starts the booking funnel and may hold inventory.
• Akamai is on every path. Both / and /en/us/fsr/choose-flights?... set _abck, bm_ss, bm_s, bm_mi, and akacd_NS_AB cookies on the first response. A datacenter-IP session will be challenged on the second navigation. A residential-proxy browserless_agent call (proxy repeated on every call) is the minimum viable config.
• Pure SPA — no embedded results state. A plain non-proxied fetch / goto of the deep-link returns the React shell HTML (~75 KB) with zero flight data embedded. There is no scraping shortcut that skips the browser; you must let the page hydrate. Verified by grepping the fetched body for searchContext|fareFamily|cabinClass|currentSearchCriteria — zero matches.
• /api/flight/recentSearch returns 405 Method Not Allowed to GET. The endpoint exists internally but only accepts authenticated POSTs from the SPA's signed-session context. Don't waste time trying to reverse-engineer United's internal searchFsr JSON endpoint — it's behind anti-tamper headers + session cookies that aren't reproducible from an out-of-band fetch. Drive the browser instead.
• /api/airports/lookup/search returns 404. The airport-typeahead endpoint is not at the obvious path. If you need IATA-code lookup, use a static IATA table (carry one in the skill harness) rather than trying to hit a United-side resolver.
• Date format must be YYYY-MM-DD. The URL parser accepts 2026-07-15; anything else (07/15/2026, 15-Jul-2026, ISO with timezone) silently drops back to the date-picker overlay.
• tt=1 is round-trip, tt=0 is one-way, tt=2 is multi-city. Counter-intuitive direction. tt=2 requires a different param layout (f1/t1/d1, f2/t2/d2, ...) and is out of scope for this skill.
• Cross-month / past dates → date-picker re-opens. If the date-picker overlay re-appears instead of cards rendering, the requested date was rejected. Common causes: date in the past, date > 11 months out (UA's booking window), or wrong format.
• taxng=1 is important. Without it, the listed prices are base-fare-only (no taxes/fees), which gives misleadingly low quotes. Always include it for "what does this cost?" queries.
• * on prices = Saver / mixed-cabin fare. Strip the asterisk when emitting numeric prices; surface as flags: ["saver"].
• "No flights available" is a valid success. Combinations like (very short window) + (small regional pair) + (high cabin class) frequently return an empty grid. Emit success: true, results: [], no_flights_for_dates: true — not a failure.
• The deep-link can also accept noflex=true to disable the flexible-date calendar above the grid (saves ~1s on hydration). Optional.
• Award-mile pricing is on a different URL. /ual/en/us/flight-search/book-a-flight/results is the award flow; do not confuse the two surfaces — they have different fare models, different cabin enums, and a different results DOM.
• Round-trip cards only show outbound on the first page. The return-leg grid only renders after an outbound is selected, which is a click this skill must NOT make. If both legs are needed, do two one-way searches and combine client-side.

Expected Output

{
  "success": true,
  "trip_type": "round-trip",
  "origin": "SFO",
  "destination": "JFK",
  "depart_date": "2026-07-15",
  "return_date": "2026-07-22",
  "passengers": 1,
  "cabin": "economy",
  "results_url": "https://www.united.com/en/us/fsr/choose-flights?f=SFO&t=JFK&d=2026-07-15&r=2026-07-22&tt=1&sc=7&px=1&taxng=1&clm=7&st=bestmatches",
  "results": [
    {
      "depart_time": "08:30",
      "depart_airport": "SFO",
      "arrive_time": "17:05",
      "arrive_airport": "JFK",
      "next_day_arrival": false,
      "duration": "5h 35m",
      "stops": 0,
      "flight_numbers": ["UA 232"],
      "cabin_class": "Economy",
      "fare_brand": "Basic Economy",
      "price_usd": 348.2,
      "flags": []
    },
    {
      "depart_time": "10:15",
      "depart_airport": "SFO",
      "arrive_time": "21:48",
      "arrive_airport": "JFK",
      "next_day_arrival": false,
      "duration": "8h 33m",
      "stops": 1,
      "flight_numbers": ["UA 481", "UA 1722"],
      "cabin_class": "Economy",
      "fare_brand": "Economy",
      "price_usd": 412.4,
      "flags": ["saver"]
    }
  ],
  "no_flights_for_dates": false,
  "error_reasoning": null
}

Distinct outcome shapes:

// Success — flights returned (canonical case)
{ "success": true, "results": [ /* ≥1 flight */ ], "no_flights_for_dates": false, "error_reasoning": null, ... }

// Success — no flights for the requested dates / cabin / route
{ "success": true, "results": [], "no_flights_for_dates": true, "error_reasoning": null, ... }

// Failure — Akamai challenge (challenge terminal, retry with a fresh residential-proxy browserless_agent call)
{ "success": false, "results": [], "error_reasoning": "akamai_challenge", ... }

// Failure — invalid input (unrecognized IATA, malformed date, past date)
{ "success": false, "results": [], "error_reasoning": "invalid_input: <field>=<value>", ... }

// Failure — site error banner ("We're unable to process your request")
{ "success": false, "results": [], "error_reasoning": "site_error_banner", ... }