Yes—see the groundspeed needed to keep pace with sunrise or sunset, why latitude matters, and when airliners or supersonic jets can do it.
Yes. In real-world aviation, a sufficiently fast aircraft flying west can hold the Sun near the horizon or make it appear to move backwards. It must match the westward movement of local solar time: about 902 knots at the equator, falling with latitude. Supersonic jets can; ordinary airliners usually cannot.
How fast must an aircraft fly to keep the Sun stationary?
The approximate westward groundspeed required is 902 × cos(latitude) knots. This comes from the Earth's rotation relative to the Sun over a 24-hour solar day.
| Latitude | Required westward groundspeed |
|---|---|
| 0° | 902 knots |
| 30° | 781 knots |
| 45° | 638 knots |
| 50° | 580 knots |
| 60° | 451 knots |
| 70° | 308 knots |
These are idealised figures for a due-west track that remains at the same latitude. If the aircraft is flying south-west or north-west, only the westward component of its velocity counts. At high latitudes, seasonal polar day or polar night may also mean there is no sunrise or sunset to follow.
A mistake we see constantly is comparing the required figure with indicated airspeed on the flight deck. This calculation uses groundspeed, as explained in our guide to how knot measurements separate airspeed from groundspeed. IAS and Mach describe different performance references; our explanation of why IAS and Mach are not interchangeable with groundspeed covers that distinction.
Can a commercial airliner keep pace with sunset?
A commercial airliner can theoretically match sunrise or sunset at sufficiently high latitude, but it normally falls short nearer the equator. A jet making a 500-knot westward groundspeed reaches the mathematical break-even point at about 56° latitude.
For scale, our realistic A320 speed and altitude figures show why an airliner operates in the hundreds of knots rather than near the 902 knots required at the equator. Wind matters as much as cruise performance: a westbound headwind reduces groundspeed, while a tailwind increases it.
Even when the jet is not quite fast enough, it can slow the apparent sunset dramatically. At 50° latitude, a due-west groundspeed of 500 knots is about 86% of the required 580 knots. Under ideal geometry, one hour of local solar-time change would then take roughly seven clock hours.
Supersonic aircraft can exceed the requirement over a much wider range of latitudes. A Concorde-class aircraft could make the Sun appear to reverse direction, but maximum speed alone is not enough: the aircraft must sustain that groundspeed on the correct track while carrying sufficient fuel. No aircraft can follow the terminator indefinitely without operational and fuel support.
Do you fly east or west to follow sunrise or sunset?
An aircraft must fly west to remain near either sunrise or sunset. The Earth rotates eastwards, so the sunrise and sunset boundaries move westwards across the surface.
- Flying west more slowly than the required speed makes sunrise or sunset progress more slowly.
- Matching the required westward speed holds the Sun at approximately the same elevation.
- Exceeding that speed makes local solar time run backwards, so a set Sun can reappear.
- Flying east advances local solar time faster and brings the next sunrise or sunset sooner.
For sunrise, an exact match holds the aircraft in dawn. Flying faster westward takes it back towards night; flying more slowly allows the Sun to continue rising.
Does cruising altitude help an aircraft beat sunset?
Altitude postpones sunset once, but it does not remove the need for westward speed. Climbing lowers the visible horizon, allowing an aircraft to regain sight of a Sun that has already set for an observer on the ground.
At roughly 35,000 feet, the geometric horizon is about 3.3° below the aircraft's local horizontal. The resulting time gain varies with latitude, season and atmospheric refraction. Once the aircraft levels off, the Sun resumes its apparent movement unless the flight also has enough westward groundspeed.
The speed formula ignores the tiny increase in rotational radius at altitude. At normal airline cruising levels, that correction is less than about 0.2% and does not change the practical answer.
Can passengers see two sunsets on one flight?
Yes. A passenger can see sunset, regain the Sun during a climb or sufficiently fast westbound flight, and then watch it set again after the aircraft slows, descends or changes direction.
Crossing the International Date Line is not what causes this effect; that changes the calendar date, not the Sun's physical position. The repeated sunset comes from crossing the day-night boundary or changing the height of the visible horizon.