When it comes to making aircraft that will become rapidly redundant, Boeing are no strangers to it! The Boeing 720 was marketed as a domestic variant of its groundbreaking Boeing 707, but quickly became obsolete when it decided that it would be easier to build a completely separate domestic jet airliner.
Upon its launch in 1958, the Boeing 707 was immediately lauded for its beauty, power and performance, being able to outdo even the most advanced turboprops of the time. Very quickly it had established itself with a majority of the world’s flag carriers and soon became an integral part of their long-haul fleet. However, Boeing’s reign on the domestic market was still being lost to the Turboprops as the 707 was unable to land at many airports due to its size and requirements for a lengthy runway. Boeing however had thought ahead somewhat, and planned in July 1957 a domestic version of the smallest 707 variant the 707-120.
Originally, this new aircraft was designated 707-020, but was quickly changed to Boeing 720 at the request of United Airlines so as to avoid confusion. At one point in the development phase, it was known as the 717-020, although this was the Boeing model designation of the KC-135 and remained unused for a commercial airliner until it was applied to the MD-95 following Boeing’s merger with McDonnell Douglas in 1997.
Compared to the 707-120, it has four fewer frames in front of the wing and one fewer aft: a total length reduction of 8ft 4 inches. The new model was designed to a lower maximum takeoff weight with a modified wing and a lightened airframe. The wing modifications included Krueger flaps outboard of the outboard engines, lowering take-
off and landing speeds, thus shortening runway length requirements,and a thickened inboard leading edge section, with a slightly greater sweep. This modification increased the top speed over the -120. It had four Pratt & Whitney JT3C-7 turbojet engines producing 12,500lbf each.
Because the aircraft systems were similar to the Boeing 707 no prototype Boeing 720 was built; any different systems were tested on the original Boeing 707 prototype, the Boeing 367-80 (better known as Dash-80). The first 720 took its maiden flight on November 23rd, 1959, and Type Certificate for the 720 was issued on June 30th, 1960. It was first put into service by United Airlines on July 5th, 1960, with 65 original models built for the airline.
The 720 was followed by the 720B in October 1960, differing from the original by the use of JT3D turbofan engines producing 17,000lbf each, therefore providing lower fuel consumption and higher thrust. The maximum takeoff weight for the 720B was increased to 234,000lb. The 720B first took to the skies on October 6th, 1960, and received certification and entered service with American Airlines in March 1961. Eventually, 89 720B’s were built in addition to the later conversions of American’s ten existing 720’s, bringing the production total to 154.
However, before the 720 was even five years old, it was already outdated when in 1963 the specifically built domestic model, the Boeing 727, was launched to universal acclaim. The 727 was much more flexible and efficient than the 720, and very soon it had displaced these aircraft from many of their mainline carrier positions. Gradual phasing out of the 720 from most major airlines was completed by the beginning of the 1970’s,
though in 1967 some 720/720B’s were used by the US military to shuttle troops to Far Eastern positions. The interior of these planes were stripped of class partitions making them appear very large inside. Some of these flights originated at Travis AFB California and flew non-stop to Japan. At least, one of the landing sites was Yokota AB, Japan. After arriving in Japan the troops were scheduled for further deployment to their final destination.
The Boeing 720 would however find further commercial life in Latin and South America, with airlines such as AeroCondor Columbia, Belize Air, Avianca and SAM Columbia. It would also find work in Africa and Europe, working for airlines such as Ethiopian Airlines, Aer Lingus, Air Rhodesia and Olympic Airways.
Additionally, one former United Airlines example, N7201U, later named ‘The Starship’, became a special charter aircraft for the use of rock bands during the 1970’s, primarily by pioneering Metal group Led Zeppelin. The seating capacity was reduced and a bar with a built-in electric organ were added, along with beds, a shower, a lounge area, a TV and video cassette player. This aircraft would continue to be used until 1979 before being dismantled at Luton Airport in 1982.
Boeing 720’s were used well into the 1980’s by many non-American carriers, the final days of many going largely unnoticed. The last known Boeing 720 was used by Pratt & Whitney Canada until 2010. Its final operational flight occurred on September 29th, 2010, the aircraft having been used as an engine testbed, replacing the company’s previous Boeing 747SP. In May 2012, the former PWC 720 was flown to CFB Trenton in Ontario to
be put on display at the National Air Force Museum of Canada.
During its career, 23 Boeing 720’s were lost, 12 of which were fatal and resulted in 175 deaths. 9 aircraft were hijacked and 1 was destroyed by a bomb mid-flight, resulting in 81 fatalities.
The first was Northwest Orient Airlines Flight 705, which broke apart over Florida on February 12th, 1963, killing all 43 aboard. The cause of the crash was determined to be an unrecoverable loss of control due to severe turbulence.
The next major crash was Pakistan International Airlines Flight 705 on May 20th, 1965, which crashed short of the runway at Cairo International Airport, killing 121 of the 127 people on board.
As mentioned, one 720 was destroyed in-flight by a terrorist bomb, this being Middle East Airlines Flight 438 on January 1st, 1976. The plane was en route from Beirut to Abu
Dhabi when the device exploded in the forward cargo compartment, killing all 81 aboard. The perpetrators were never identified, though common belief is that it was carried out by the Army of Free Lebanon, who at the time was waging a bitter civil war against the Lebanese government.
Perhaps the most spectacular crash of a Boeing 720 however took place on December 1st, 1984, when N833NA, which had been built specially for the FAA as a training aircraft, was flown by remote control from Edwards Air Force Base and crashed deliberately into the open desert to test passenger survivability by way of Crash Test Dummies being seated in the cabin. The aircraft flew a few circuits before smashing down into a designated impact zone, resulting in a spectacular fireball and massive destruction. Generally, however, the crash was deemed a complete success, even though in a real incident most of the passengers would have died horribly, as did most of the dummies!
Today sadly there are no Boeing 720’s to grace the skies. As mentioned, the last to be retired was in 2010, and those retired in the 1990’s have long since been scrapped. Four aircraft are however preserved in varying degrees, one in Columbia, one in Taiwan and one in Canada and one in Pakistan.
Though the Boeing 720 was superseded almost immediately, and made irrelevant before it was even five years old, it’s not surprising that very few people know about it. However, those who do remember it fondly as an interesting take on a domestic airliner, a four-engined jet styled to perfection, a scaled down version of Boeing’s triumphant 707, it sure ain’t no Airbus A320! Imagine flying from Edinburgh to London aboard one of these!