Boeing 720

Boeing 720
Steve Fitzgerald · GFDL 1.2 · source
Name	Boeing 720
Caption	Boeing 720 in service
Type	Short- to medium-range narrow-body jet airliner
Manufacturer	Boeing
First flight	November 23, 1959
Introduced	July 5, 1960
Retired	varied by operator
Primary user	multiple airlines

Boeing 720 is a four-abreast, narrow-body jet airliner developed as a derivative of the Boeing 707 family to serve medium-range routes with reduced weight and improved field performance. Introduced in 1960, the 720 combined elements of Boeing design with powerplants and systems intended to appeal to operators such as United Airlines, American Airlines, Pan Am, and Trans World Airlines. Its role bridged the gap between early long-range jetliners and the later generation of short-haul jets like the Boeing 737.

Development and design

The origin of the 720 traces to requirements from United Airlines and American Airlines seeking a shorter, lighter derivative of the Boeing 707 optimized for domestic and regional routes between hubs such as Chicago O'Hare International Airport, New York John F. Kennedy International Airport, and Los Angeles International Airport. Boeing engineers led by personnel from the original 707 program modified the fuselage, wing, and landing gear; they incorporated the wing from the 707-120 series with a shorter fuselage and altered trailing-edge flaps to improve low-speed handling for operations at airports like San Francisco International Airport and Denver International Airport (then Stapleton). The design team evaluated powerplants including the Pratt & Whitney JT3C and later turbofan conversions such as the Pratt & Whitney JT3D to meet performance and noise expectations influenced by regulators at agencies including the Civil Aeronautics Board and the International Civil Aviation Organization.

Structural changes included a lighter center wing box, modified auxiliary power systems used in contemporary DC-8 designs, and aerodynamic refinements tested in wind tunnels at the California Institute of Technology-affiliated facilities and university laboratories collaborating with Boeing. The 720's systems integration relied on suppliers such as General Electric for avionics components and subcontractors from the Lockheed supply chain, reflecting Cold War–era industrial networks involving firms like North American Aviation and Douglas Aircraft Company.

Variants

Boeing marketed several distinct variants developed with input from major operators and leasing firms such as International Lease Finance Corporation and Pan American World Airways' engineering divisions. The initial production model utilized turbojet engines offered to carriers like United Airlines and Eastern Air Lines. An improved version, developed following airline feedback and the success of the Pratt & Whitney JT3D turbofan on the 707-320, was offered as a re-engined option delivering improved fuel efficiency and reduced noise to meet emerging standards from authorities such as the Federal Aviation Administration.

Civil conversions and freighter adaptations were produced for cargo specialists and integrators including FedEx and national carriers across Europe and South America, often incorporating avionics retrofits compatible with standards promulgated by organizations like the European Union Aviation Safety Agency precursor bodies. Military and governmental conversions were undertaken for VIP transport by agencies such as the United States Air Force and state operators connected to presidencies in South America and Africa.

Operational history

Major early operators included United Airlines, American Airlines, Pan Am, and Trans World Airlines, which deployed the type on domestic trunk routes and shorter international sectors linking hubs such as Miami International Airport and Latin American gateways. The 720 saw service on transcontinental missions while airlines transitioned from piston-powered fleets of Douglas DC-6 and Lockheed Constellation types to pure jets, influencing schedules and route structures negotiated with airport authorities at Chicago Midway Airport and international counterparts including London Heathrow.

Over time, secondhand markets supplied smaller carriers and charter operators like Northwest Airlines affiliates, regional flag carriers in Africa, and tour operators in Asia and Europe. Cargo conversions extended the platform's life into the 1980s and 1990s with operators such as national postal services and freight forwarders. Preservation groups and museums, including institutions in Seattle and Kansas City, have conserved examples to illustrate the jet age transition after retirements by flag carriers and charter lines.

Technical specifications

Typical specifications reflected the 720's role as a shortened derivative with reduced maximum takeoff weight and range relative to the longer 707 variants. Powerplant options evolved from turbojet installations to turbofan retrofits such as the Pratt & Whitney JT3D, while systems updates paralleled developments in avionics by firms like Honeywell and Collins Aerospace. Performance parameters were tuned for operations at medium-altitude airports and busy terminals including O'Hare and JFK, with considerations for climb gradients used in procedures published by authorities such as the Federal Aviation Administration and airway manuals from Airline Operators Committee equivalents.

Airframe features included a conventional low-wing cantilever monoplane layout, four underwing pods, and a pressurized cabin outfitted by cabin completion houses historically linked to Iraqi Airways and other national carriers. Weight-saving measures and structural reinforcements balanced durability with payload flexibility demanded by cargo conversions and VIP completions undertaken for government delegations and corporate flight departments linked to multinational firms headquartered in cities such as New York City, Chicago, and Los Angeles.

Operators and civil service

Primary legacy operators encompassed major U.S. carriers and international airlines across Europe, Latin America, and Africa. Airlines that placed early orders included United Airlines and American Airlines, while Pan Am and Trans World Airlines used the type for network feed and supplemental capacity. Leasing companies and smaller scheduled operators, including flag carriers of countries such as Brazil and Mexico, incorporated the 720 for domestic and regional services. Over decades, cargo specialists, government flight units, and charter operators kept examples flying after mainline retirement, with support from maintenance organizations in aviation hubs like Miami, Los Angeles, and Paris Charles de Gaulle Airport.

Accidents and incidents

The 720 experienced accidents and incidents during its operational life involving airlines such as National Airlines (1934–1980), Pakistan International Airlines, and regional operators; occurrences ranged from runway overruns at airports like Newark Liberty International Airport to hull losses in varied environments. Investigations were conducted by agencies including the National Transportation Safety Board and international counterparts, resulting in recommendations to operators and regulatory authorities including the Civil Aeronautics Board successor bodies. Some high-profile events led to retirements of airframes and influenced fleet management decisions at carriers such as American Airlines and United Airlines.

Category:Aircraft of the United States