Boeing 737-400 vs. McDonnell Douglas MD-11

The Boeing 737-400, part of the 737 Classic series, is a narrow-body, twin-engine airliner developed to meet the evolving requirements of the short to medium-haul market. First introduced in 1988, the 737-400 expanded upon the success of its predecessor, the 737-300. The -400 variant entered manufacturing shortly after finalization of design plans between Boeing and launch customer Piedmont Airlines (later merged into US Airways). It gives increased capacity and range, offering an option in between Boeing's 737-300 and the 757-200.

The fuselage incorporated a key 8 foot expansion to enable typical accommodation for up to 170 passengers in a 2-class layout. Other changes included increased weights and structural reinforcements, enhanced avionics/flight controls, and higher thrust CFM powerplants required for the heavier max takeoff figures. Cost efficiencies were achieved keeping cockpit continuity with the ubiquitous 737 flight deck suite.

Spanning 119.6 feet (36.5 meters) in length with a wingspan of 94.5 feet (28.8 meters), the 737-400 was designed to accommodate the growing demand for larger single-aisle aircraft. The aircraft typically seats 144 passengers, providing more space and comfort compared to earlier models in the series. This increased capacity made the 737-400 an attractive option for airlines seeking to transport more passengers on popular routes, without the need for a larger, wide-body aircraft. Equipped with two CFM International CFM56-3C1 engines, the 737-400 delivers a total thrust of 44,000 lbf (196.0 kN). This engine configuration, combined with a fuel capacity of 5,310 US gallons (20,100 liters), allows the aircraft to achieve a range of 2,079 nautical miles (3,850 kilometers).

In the competitive commercial aviation market of its time, the Boeing 737-400 contended with models like the McDonnell Douglas MD-80 series. Its introduction marked another milestone for Boeing in the evolution of the 737 family, solidifying the company's position in the market for short to medium-haul airliners. Airlines such as Alaska Airlines, Turkish Airlines, and British Airways incorporated the Boeing 737-400 into their fleets. The aircraft's operational role was significant, enabling these carriers to expand their route networks and increase flight frequencies, particularly in domestic and regional markets.

The McDonnell Douglas MD-11 is a wide-body, tri-jet airliner, recognized for its extended range and enhanced capabilities in long-haul commercial aviation. As a successor to the iconic DC-10, the MD-11 incorporated advanced technology and design improvements, making it a significant model in the evolution of wide-body aircraft. The MD-11 took its maiden flight in 1990, and was produced until the turn of the 21st century. There are no MD-11s servicing passenger flights today, but some MD-11 are still being used for freight operations with FedEx, UPS, and Western Global Airlines.

With a length of 61.6 meters (202.1 feet), the MD-11 is notably longer than the DC-10, which provided increased passenger and cargo capacity. This extension in length was complemented by a wingspan of 52.0 meters (170.5 feet), which included winglets for improved aerodynamic efficiency. The MD-11's was equipped with GE CF6-80C2s or PW4000 turbofan engines, which delivered a total maximum thrust of 822.0 kN (123,000 lbf). With a substantial fuel capacity of 146,173 liters (38,615 US gallons), the MD-11 boasts a range of approximately 12,455 kilometers (6,725 nautical miles), enabling it to operate on intercontinental routes with ease.

The MD-11 comfortably accommodated 298 passengers, and could be designed to fit over 340 in a higher density configuration. The most common configurations for the twin aisle jet included 9 seats to a row (3-3-3 or 3-4-2).

In the competitive landscape of long-haul airliners, the McDonnell Douglas MD-11 was positioned as an alternative to models like the Boeing 747 and the Lockheed L-1011 TriStar. By 2004, most carriers that utilized the MD-11 for long-haul passenger routes had replaced it with the Airbus A330, A340, and Boeing 777. When Boeing acquired McDonnell Douglas in 1997, it ultimately created internal competition for the MD-11 with the 767 and 777. A lack of interest from the market also lead to Boeing cutting production for the commercial variant short, while the freight version was continued for slightly longer.

KLM, Swissair, and Delta Air Lines were among the airlines who utilized the aircraft's range and capacity to expand their international route offerings. The MD-11's operational role was characterized by its ability to efficiently serve long-haul routes, offering a blend of passenger comfort and operational economics. Some airlines like China Eastern Airlines and Korean Air had converted their MD-11 aircraft into freighters rather than selling or retiring them.

The MD-11's production and service history reflect its role as a pivotal model in the wide-body aircraft segment. Its design and technological advancements, including the use of winglets and a glass cockpit, marked important steps in the advancement of commercial aircraft design. Although its production was eventually surpassed by more modern aircraft, the MD-11 remains a notable aircraft in the history of aviation, particularly for its contributions to long-haul air travel.