Flight time: Seattle to Sydney

Route details

Distance breakdown: Seattle to Sydney

The 12,472-km great-circle distance between Seattle (47.45°N, 122.31°W) and Sydney (-33.95°N, 151.18°E) spans 81.4° of latitude and 273.5° of longitude, trending primarily east. In miles, this is 7,750 mi or 6735 nautical miles. The great-circle path — the shortest distance over Earth's curved surface — is calculated using the Haversine formula from the two airports' precise coordinates.

Cruise speed and flight phases

On this 12,472-km long-haul route, aircraft spend the majority of the 14h 21m to 16h 03m journey at optimal cruise altitude of 35,000–42,000 feet, where modern wide-body jets achieve true airspeeds of 820–900 km/h (Mach 0.82–0.86). The initial climb and final descent represent a smaller fraction of total flight time compared to shorter routes. Aircraft like the Boeing 777, 787, or Airbus A350 typically operate routes of this distance, with step climbs during the flight to reach progressively more efficient altitudes as fuel burns off and the aircraft lightens.

Ground time and routing overhead

Our 30–50 minutes overhead allowance covers: taxi-out at SEA, takeoff and initial climb, descent and approach at SYD, and taxi-in to the gate. SEA is a major international hub where taxi times of 15–25 minutes are common during peak periods. At SYD, arrival taxi and gate assignment can add 10–20 minutes, especially during busy arrival banks. Oceanic tracks between Seattle and Sydney follow organized route systems (like the North Atlantic Track system) that may add 5–10% to the theoretical great-circle distance. These tracks are assigned daily based on forecast winds.

Return flight: Sydney → Seattle

The return flight from Sydney to Seattle differs noticeably in duration due to upper-atmosphere wind patterns along this oceanic corridor. The jet stream — a high-altitude river of fast-moving air flowing generally from west to east — creates an asymmetry: the eastbound leg (Seattle to Sydney if eastbound, otherwise Sydney to Seattle) is typically 20–60 minutes shorter. Airlines adjust fuel loads and even routing to account for this, sometimes flying more southerly or northerly tracks on the headwind leg to minimize the impact. Over a year, the average time difference between the two directions on this specific route is estimated at 30–45 minutes.

Seasonal variation in flight times

Flight times between Seattle and Sydney vary modestly by season — typically 10–20 minutes. Upper-level wind patterns shift with the seasons: winter generally brings stronger westerly winds at these latitudes, while summer patterns are more variable. Thunderstorm activity along the route corridor peaks in summer months, occasionally causing routing diversions that add distance. Winter operations may include de-icing delays at SEA, which extend the overall gate-to-gate time.

Airport information

Seattle-Tacoma International Airport (SEA) is a major international hub in Seattle, United States. As a tier-1 airport, it handles high traffic volumes, which means longer average taxi times but also higher flight frequency and competition that can benefit travelers on pricing. Sydney Kingsford Smith Airport (SYD) is a major international hub in Sydney, Australia. As a tier-1 airport, it handles high traffic volumes, which means longer average taxi times but also higher flight frequency and competition that can benefit travelers on pricing.

Flight times from Seattle to other destinations

Flight time FAQ: Seattle to Sydney