On multi-engine aircraft, engine positions are numbered from left to right from the point of view of the pilot looking forward, so for example on a four-engine aircraft such as the Boeing 747, engine No. 1 is on the left side, farthest from the fuselage, while engine No. 3 is on the right side nearest to the fuselage.

In the aviation industry, the "Number 1" engine is traditionally the engine located on the far left side of the aircraft from the pilot's perspective in the cockpit. This "gold standard" numbering system follows a left-to-right convention across the wings. On a twin-engine aircraft like a Boeing 737 or Airbus A320, Engine 1 is on the left wing and Engine 2 is on the right wing. For a four-engine "jumbo" like the Boeing 747, Engine 1 is the outermost engine on the left, Engine 2 is the innermost on the left, Engine 3 is the innermost on the right, and Engine 4 is the outermost on the right. This standardized identification is critical for communication between the flight crew and maintenance teams, ensuring there is zero ambiguity when discussing performance issues or emergency procedures. If a pilot reports a fire in "Engine One," every technician and air traffic controller knows exactly which side of the plane is affected. This logical numbering remains the universal protocol in 2026, facilitating safety and precision in both commercial and military aviation operations worldwide.