Flight Time Calculator
Estimate flight duration and time zone arrival time for long-haul routes.
MCA Yachtmaster Ocean, MNZ Coxswain (restricted)
Offshore sailing instructor and maritime educator with 30 years of blue-water passages. Author of coastal navigation guides for NZ waters.
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About the Flight Time Calculator
Commercial flight times are primarily determined by distance and the jet stream — a band of high-altitude winds at 9,000–12,000 metres that flows west to east across the North Atlantic and Pacific. Westbound flights fight headwinds that can reduce ground speed by 100–200 km/h; eastbound flights ride tailwinds that can increase it by the same amount. This is why a London to New York flight takes around 8.5–9 hours eastbound but only 7–7.5 hours westbound — not a scheduling anomaly but basic physics. The jet stream's position and strength varies seasonally, which is why winter transatlantic crossings are sometimes significantly faster or slower than summer averages.
Modern wide-body jets (Boeing 787, Airbus A350) cruise at approximately 900–950 km/h at altitudes of 10,000–13,000 metres, where the thin air reduces aerodynamic drag. For a given route, airlines file specific flight plans that route around weather systems and optimise for fuel efficiency rather than pure speed. The actual gate-to-gate time includes taxi time at departure (15–45 minutes), climb to cruise altitude (30–45 minutes), descent and approach (30–45 minutes), and taxi at arrival — adding roughly 2 hours to the pure flying time for a long-haul route.
Jet lag occurs because the body's circadian rhythm — governed by the suprachiasmatic nucleus in the hypothalamus — is synchronised to your home time zone and cannot adjust instantaneously. The general rule is approximately 1–1.5 days of adjustment per hour of time zone change, though eastbound travel is consistently harder than westbound: most people's internal day runs slightly longer than 24 hours (approximately 24.2 hours), making it easier to extend the day (westbound) than compress it (eastbound). Exposure to natural light at the destination time zone is the most powerful tool for resetting the circadian clock.
Tips to improve your result
- 1.
For westbound transatlantic flights, take the morning flight if possible — you arrive with time to have an evening at the destination, stay up until local bedtime, and wake feeling mostly adjusted. Afternoon flights land at dinnertime but your body is at 3 am, making the first day harder.
- 2.
To minimise jet lag: start adjusting sleep time 2–3 days before departure (shift earlier for eastbound, later for westbound), avoid alcohol and excess caffeine on the flight (both disrupt sleep architecture), drink plenty of water (cabin humidity is 10–15%, much lower than typical indoor air), and use melatonin at destination bedtime for the first 2–3 nights (0.5–3mg is effective; larger doses don't improve jet lag and may cause grogginess).
- 3.
The CO₂ figure shown (approximately 115kg per economy seat per 1,000km) reflects economy class radiative forcing including non-CO₂ effects at altitude. Business class passengers have approximately 3× the per-seat footprint due to larger seat space consuming more of the aircraft's payload capacity.
- 4.
Long-haul economy flights are dehydrating and can cause lower-limb oedema (swelling). Compression socks, drinking water every 1–2 hours, and walking/stretching every hour significantly reduce deep vein thrombosis (DVT) risk on flights over 6 hours. The risk is highest in the 24 hours post-flight when passengers are likely sedentary.
- 5.
Seat selection: seats at the exit row and bulkhead have more legroom but often fixed armrests (can't lift). Seats at the back of the plane are louder (closer to engines) but tend to have more availability. Seats over the wing experience less turbulence motion (closer to the aircraft's centre of gravity).