flight-connection-risk-analyzer

Use when booking or sweating a connecting flight: computes true connection budget from minimum-connect-time by airport/terminal, transfer logistics (trains, security re-entry), time-of-day delay stacking, and last-flight-of-day exposure. Verdicts SAFE / TIGHT / HIGH RISK plus a survive-the-layover protocol and rebooking rights.

Overview

Every traveler eventually stares at a booking screen asking: is a 45-minute connection at O'Hare insane, or fine? Airlines will happily sell it — they compute against the legal minimum connect time (MCT), the fastest possible wheel-stop-to-departure a marathon runner with no bag could achieve. MCT is not a plan; it's a floor. What actually decides whether you make a connection:

1. Buffer above MCT — scheduled time minus the legal minimum.
2. Terminal transfer reality — some airports require a train, a bus, or exiting and re-clearing security (international arrivals into the US always do: customs + bag recheck + TSA again).
3. Delay stacking — on-time performance collapses through the day. A 6 AM flight departs on time ~90% of the time; the 7 PM departure of the same route inherits every delay of the aircraft's previous legs (~65–70%).
4. Consequence asymmetry — miss the last flight of the day and the "inconvenience" is a hotel you pay for; on a self-transfer (separate tickets) the airline owes you nothing and you buy a new walk-up fare.

This skill turns those four factors into a 0–100 risk score, a verdict, and a protocol. It does not book anything and never claims real-time data — it is a planning instrument used before you click purchase.

When to Use

• Booking any itinerary with a connection and judging whether the layover is sane
• Deciding between "1h05 at hub X" vs "2h40 at hub Y" vs paying more for nonstop
• Self-transfer itineraries (separate tickets / budget-carrier hops) — the 3-hour doctrine
• International arrivals into the US (customs + recheck + re-security math)
• Already booked a tight connection and wanting the survive-it protocol
• "What happens if I miss it?" — same-ticket protection vs separate-ticket ruin

Don't use for: real-time "will my flight make it today" (check the airline app / FlightAware), or visa/transit-permit questions (see border-buddy).

The Four-Factor Model

1. Connection buffer (the floor)

text

buffer = layover_minutes − MCT(airport, itinerary type)

MCT varies by airport AND by itinerary type (domestic→domestic, dom→intl, intl→dom, intl→intl) AND sometimes by terminal pair. Typical legal minimums:

Pattern	Typical MCT	Notes
Domestic → domestic, same terminal	30–40 min	DL@ATL 35, AA@DFW 40, UA@ORD/DEN 45
Domestic → domestic, terminal change	45–60 min	JFK T2→T4 style
Domestic → international	60–90 min	Boarding closes earlier; docs check
International → domestic (US entry)	90–120 min	Customs + bag recheck + TSA
International → international (same alliance, sterile transit)	50–75 min	AMS/MUC/IST efficient
Self-transfer (separate tickets)	no MCT protection	Plan ≥ 3h; first ticket's delay is your problem

2. Terminal transfer time

The script carries a per-hub table (walk / train / bus / re-security) for ~25 major hubs. Examples baked in: ATL concourse train 10–15 min; ORD Terminal 5 (intl) ↔ Terminals 1–3 via ATS train 25–40 min plus security re-entry; JFK AirTrain between terminals 20–45 min; LHR T4↔T5 not walkable (~25–35 min); CDG 2E↔2G shuttle bus ~20 min; IST, MUC, AMS walkable 15–30 min.

3. Time-of-day delay stacking (US DOT on-time curves)

Approximate departure on-time rates by scheduled departure block:

Departure block	On-time (≈)	Delay inheritance
05:00–07:00	88–92%	aircraft usually fresh
08:00–11:00	84–88%
12:00–15:00	78–84%
16:00–19:00	70–78%	cascading
20:00–23:59	62–72%	worst stack + overnight risk if missed

The inbound aircraft's departure block matters more than yours: a 9 PM connection usually rides an aircraft that has flown 4–6 legs already.

4. Consequence modifiers

• Last flight of the day to destination → miss = overnight (add +15 risk)
• Winter season (Dec–Feb) at northern hubs (ORD, DTW, DEN, MSP, JFK) → +10
• Self-transfer → +25 and no protection; budget a walk-up-fare disaster cost
• Same PNR (one ticket) → airline must rebook you; risk is hours, not dollars
• International departure missed → often next-day + visa/hotel cascade

Scoring & Verdicts

text

risk = base(buffer) + tod_penalty + last_flight + season + self_transfer
  buffer ≥ 60 min  → base 5      buffer 40–59 → 20
  buffer 25–39     → base 40     buffer 10–24 → 60
  buffer < 10 or < MCT → base 85

Score	Verdict	Meaning
0–24	SAFE	book it; normal ops you make it with time to eat
25–49	TIGHT	workable, fly the protocol below
50–74	HIGH RISK	only if no alternative; assume realistic 20–30% miss on bad days
75+	RUSSIAN ROULETTE	do not book; you are planning to miss it

Survive-a-Tight-Connection Protocol

1. Seat near the front of the inbound aircraft (rows within first ~10); deplaning last from row 38 costs 10–15 minutes.
2. Carry-on only. A checked bag on a <60 min domestic connection is a coin-flip on some airlines' ramp handling.
3. Know the terminal map before landing (the script prints transfer steps).
4. Tell the flight attendant on approach — they can radio ahead / hold 2 min.
5. On landing, do not stop; gates close 10–15 min before departure.
6. If you miss it: same ticket → get in rebooking line and open the airline app simultaneously (app often rebooks faster than the queue).
7. Self-transfer missed → you are a no-show; buy the next fare and file travel insurance / credit-card trip-delay claim if covered.

Using the Script

bash

# Domestic connection at ATL, 50 min layover, departing 18:40, not last flight
python3 scripts/connection_scorer.py --airport ATL --layover 50 \
    --type dom-dom --dep-block 16-20

# International arrival into the US connecting at ORD, 1h50, evening
python3 scripts/connection_scorer.py --airport ORD --layover 110 \
    --type intl-dom --dep-block 16-20 --season winter --last-flight

# Separate tickets (self-transfer) through LHR
python3 scripts/connection_scorer.py --airport LHR --layover 165 \
    --type intl-intl --self-transfer --dep-block 12-16

# List the hub knowledge base
python3 scripts/connection_scorer.py --list-hubs

Output: MCT used, transfer-time estimate, effective buffer, risk score, verdict, and a situation-specific protocol list.

Common Pitfalls

1. Trusting "legal connection" labels. Booking sites show itineraries at MCT + 0; legal ≠ sane. MCT assumes no line anywhere.
2. Forgetting US international arrivals re-clear security. 1h30 at ORD from an international arrival is a sprint with a re-TSA line.
3. Reading the layover as door-to-door. Deplaning (10–15 min) and boarding close (10–15 min) eat 20–30 minutes of every layover before you move.
4. Self-transfers priced like connections. Kiwi-style "connections" on separate tickets carry no protection — 3 hours minimum, and know the next fare.
5. Evening hub connections in winter. Stack two risk factors and a "workable" 50 minutes becomes a planned overnight.
6. Connecting to the last flight. The cheapest itineraries often are; multiply the miss cost by "is there a 6 AM flight tomorrow?"

Verification Checklist

• Itinerary type matches (dom-dom / dom-intl / intl-dom / intl-intl / self-transfer)
• Airport hub entry exists in the table (else use generic MCT bands + manual transfer estimate)
• Departure block of the inbound leg used for delay stacking
• Last-flight-of-day and season flags set when true
• Verdict ≤ TIGHT before booking; if HIGH RISK, a fallback flight identified
• Self-transfer: ≥ 3h layover and next-fare price known before booking