Why Most Commercial Airplanes Have Two Engines

Commercial airplanes had as many as four engines in the 1950s. However, improvements in thrust and reliability have shown over the years that two engines are reliable enough and can produce the required thrust. More engines mean more fuel consumption, which adds to the overall operating cost.

Cost Efficiency and Fuel Efficiency

The fundamental reason for having two engines is cost efficiency and fuel efficiency. If an aircraft had three engines, the cost to fly would be higher due to the acquisition cost, loss of fuel efficiency, and additional maintenance costs.

Redundancy and Safety

Everything on an airplane is planned for when it will fail. Redundancy is the key here. On takeoff roll, if an engine fails after V1, the remaining engine alone is enough to complete the takeoff climb and return to the airport for a safe landing. This is a critical safety feature.

During long-haul flights, if one engine fails at cruising altitude, the aircraft can still rely on the remaining engine to find the nearest suitable airport and land safely. This is a vital safety mechanism. It is important to note that having two engines also increases the life of those same engines by having two perfectly working engines doing the work of one. This also increases fuel efficiency as you won't need a single engine working as hard under those conditions.

Single Engine Aircraft: A Quirky Concept

There are literally thousands of airplanes that have just one engine. However, this concept is not as common in commercial aviation as it might seem. Jets with two or more engines suggest air transport aircraft carrying much larger cargo loads and/or passengers. The greater weight demands more power and the enhanced safety factor with more engines.

A single engine jet transport would be difficult if not impossible to design, build, and still have the traveling public’s acceptance in commercial aviation. Nor would it have the safety element of multiple engines. Most commercially operated aircraft, working as an aviation-related entity as opposed to the commercial airline industry in this present day, mostly utilize twin engine airplanes from various manufacturers.

In summary, the choice of two engines in most commercial airplanes is a result of balancing cost efficiency, fuel efficiency, and safety. Two engines provide the necessary redundancy to ensure safety and reliability during critical flight phases.