# Travel Connection Checker

> Estimate your odds of making a flight connection, step by step. Enter your arrival and onward departure times and what you have to do in between (terminal change, passport control, security, baggage). The checker adds up transparent time ranges for each step, compares them with your connection time and estimates the chance of making it under a simple inbound-delay model. It is an estimate, never a guarantee.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://travelconnectionchecker.usefulweb.site/ (interactive tool at https://travelconnectionchecker.usefulweb.site/tool)
- JSON API: POST https://travelconnectionchecker.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://travelconnectionchecker.usefulweb.site/api/v1/tool)
- OpenAPI: https://travelconnectionchecker.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://travelconnectionchecker.usefulweb.site/mcp - tool `travel_connection_checker`

## Inputs
- arrival (datetime, required): Scheduled arrival (local)
- departure (datetime, required): Scheduled onward departure (local, same airport)
- terminalChange (boolean): Terminal change
- immigration (boolean): Passport / immigration check
- securityRecheck (boolean): Security screening again
- baggageRecheck (boolean): Collect and re-check baggage
- airportSize (select): Airport size
- walkingSpeed (select): Walking speed
- gateClosesMinutes (integer): Gate closes before departure - Check your boarding pass; often 10–20 minutes.
- onTimeProbability (number): Inbound flight on-time probability - Planning default; replace with the route’s on-time record if you know it.
- meanDelayMinutes (number): Average delay when late
- officialMct (integer): Official minimum connection time (if known) - From the airline/airport for your connection type.

## Method
- Available time = scheduled departure − scheduled arrival − gate-closure minutes.
- Required time = deplaning + walking (+ terminal change) + optional immigration, security and baggage re-check, each an editorial [best, typical, worst] range by airport size; walking and terminal transfer are multiplied by 1.4 (slow) / 1.0 / 0.8 (fast).
- Buffer = available − required, for each of best/typical/worst.
- Inbound delay model: on time with probability p, otherwise delay ~ Exponential(mean delay). P(miss) = (1 − p)·e^(−buffer/mean) if buffer ≥ 0, else 100%. P(make) = 1 − P(miss). Early arrivals and onward-flight delays are ignored (both would help).
- Overall chance: total processing time is treated as a triangular distribution between the best, typical and worst totals, and P(make) is averaged over it numerically (400 slices). The best/worst columns show the chance if processing is at its fastest/slowest.
- Verdict from the overall chance: ≥ 95% comfortable, ≥ 85% ok, ≥ 70% tight, ≥ 50% risky, below that very risky.

## Limits
- A planning estimate from simplified assumptions — not a guarantee. Airline, airport and border procedures and queues vary widely.