Two views of the same journey
The trip baseline uses a neutral traveler profile. Your difficulty applies your sleep ability, normal schedule, chronotype, sensory sensitivity, recovery, connection confidence, preferred buffer, height, stiffness, jet lag history and arrival-day demands. Showing both makes the effect of personalisation visible.
The six-factor model
Each component is calculated from 0 to 100 and then weighted. The functions are deliberately non-linear: a dangerously short connection should become difficult faster than a comfortable one, and a time-zone shift from one to six hours should not behave like a simple flat points-per-hour rule.
Journey Load
Flight time, elapsed time, distance and number of segments.
Sleep Disruption
Overlap with normal sleep, overnight timing and ability to rest onboard.
Circadian / Jet Lag
Time-zone difference, east/west direction and past personal response.
Connections
Number, duration, airport changes, experience and preferred buffer.
Physical Comfort
Hours seated, cabin, exact seat product, position, height and stiffness.
Schedule Stress
Early starts, night departures, overnight arrivals and arrival-day demands.
Time zones, distance and seats
Airport coordinates and IANA time-zone identifiers come from the MIT-licensed airportsdata project. The browser converts local airport times to UTC with daylight-saving rules, calculates straight-line distance with the haversine formula, and samples flight time against the traveler’s normal sleep window.
Cabin and seat product are separate. Economy can mean standard, extra legroom, exit row or bulkhead. Premium cabins distinguish recliner, lie-flat and suite-style products. These are functional categories—not claims about a specific airline seat.
Evidence used as direction, not false precision
The model follows established direction-of-effect findings: sleep loss and circadian misalignment contribute to fatigue; the strongest circadian sleep drive often occurs in the biological night; larger time-zone shifts create more jet lag; and eastward adjustment is often slower than westward. The exact 0–100 mapping and weights are TravelDifficulty’s own planning model.
CDC Yellow Book: Jet Lag Disorder
The CDC describes jet lag as temporary desynchronisation after rapid time-zone travel, identifies the number of time zones and individual factors as risks, and notes average adaptation around one hour per day eastward and 1.5 hours westward. View source.
FAA fatigue and circadian guidance
The FAA describes sleep loss, circadian timing and individual morning/evening preference as relevant to fatigue and alertness. View source.
What the score does not know
Version 1.1 does not include live delays, airport queues, airline-specific minimum connection times, terminal walking distances, aircraft-specific pitch or width, medical conditions, medication, alcohol, exact sleep obtained, trip purpose or the traveler’s condition on the day. It should support a booking decision—not replace airline guidance or professional health advice.
How the model will improve
Future versions can add airport-specific connection data, aircraft and seat-map information, live schedules and historical punctuality. Material formula changes should receive a new model version and remain documented here. External review by sleep, circadian and aviation specialists would be a meaningful next step before making stronger evidence claims.