When it comes to measuring speed at sea and in the air, knots are the standard unit. But why do ships and aircraft use knots instead of more familiar units like kilometers per hour or miles per hour? The answer lies in history, practicality, and the unique demands of navigation.

The term “knot” comes from an old method sailors used to measure speed. They would tie knots at regular intervals along a rope and let it run out behind a ship. By counting how many knots passed through their hands in a set amount of time, they could estimate the vessel’s speed. This method, called the “log line,” became a standard practice for centuries and gave the unit its name.

Today, modern technology has replaced the log line, but the knot remains the official speed unit for maritime and aviation navigation. One knot equals one nautical mile per hour. A nautical mile is slightly longer than a standard mile and is based on the Earth’s geometry, making it especially useful for navigation across long distances and for plotting courses using latitude and longitude.

In aviation, knots are used for the same reason. Aircraft navigation relies on charts, airways, and distances measured in nautical miles. Using knots ensures consistency with maritime standards, which is especially important for flights over oceans and international airspace. Pilots, air traffic controllers, and weather reports all rely on knots to communicate speed clearly and accurately.

Wind speeds are also commonly reported in knots, both for ships and aircraft. This provides a consistent way to describe the effect of wind on travel and navigation. Whether it’s a gentle breeze or a strong storm, knowing the speed in knots helps sailors and pilots plan routes and maintain safety.

Typical cruising speeds vary by vessel and aircraft. Modern cargo ships often travel around 20–25 knots, while passenger ferries can reach 30–40 knots. Commercial airliners cruise at roughly 450–500 knots, depending on altitude and weather conditions. Military jets, of course, can go much faster, but even supersonic aircraft may still use knots for consistency in navigation.

Knots are more than a historical relic—they are a practical, internationally recognized standard that connects past and present navigation. By understanding knots, we gain insight into how sailors and pilots measure speed, plan routes, and maintain safety over the vast oceans and skies.