Last month marked the 40th anniversary of the entry into service of the Lockheed L1011 TriStar, the last commercial aircraft programme of famous US manufacturer Lockheed Aircraft Corporation. The trijet was developed to take advantage of new propulsion innovations to enable more passengers to fly on medium- and long-haul routes, although it was ultimately further developments from engine producers that marked the end of its life cycle as new more efficient twin engine designs came on to the market.

Although a small number of TriStars remain in service with the military and with ACMI charter operators in developing markets, there have been no scheduled air services with type since May 2008. The HUB takes a look back at the TriStar programme and using information from the Schedules iNet historical database of our fellow UBM Aviation brand, OAG, we highlight the declining scheduled operations with the classic trijet over the past 30 years.

When the Lockheed L1011 TriStar was first launched, it was the most technologically-advanced aircraft in the world. However, despite the manufacturer having a sound pedigree in the commercial aviation market with models such as the Super Constellation of the 1950s and the Electra of the 1960s, it was never able to translate its propliner success into the commercial jet arena. Fierce competition diluted the market, with the rival Douglas DC-10 trijet making its first flight just eleven weeks before the TriStar, while the emergence of the more efficient twin-engined Airbus A300 widebody in the early 1970s and an economic recession the same decade meant that the aircraft was never able to fulfil its potential.

Work on the project dates back to the 1960s when American Airlines approached Lockheed and rival Douglas Aircraft Corporation with a requirement for a medium-to-long range widebody passenger jet. Lockheed was prudent not to put all their eggs in one basket, aware that American’s requirements for the new aircraft were not shared by the overall market. The US carrier was happy to offer one-stop transcontinental domestic flights with more interest in carrying the maximum number of passengers at the lowest seat mile costs, owing to capacity and operational constraints at its New York/Lau Guardia base.

An original twin-engine design developed by Lockheed to meet American’s plans soon developed into a trijet as Eastern Airlines and Trans World Airlines (TWA) started talking about the need of a high-density, long-range airliner. Both airlines required the third powerplant to overcome geographical problems, Eastern to operate over long stretches of water and TWA to cross the Rocky Mountains. TWA had only recently introduced its first Boeing 747 models into service but was finding the aircraft too large and ultimately uneconomical for its Chicago-Los Angeles flights and connections to West Coast cities from its Kansas and St Louis hubs.

On February 19, 1968 American Airlines confirmed its selection of the DC-10 ahead of the TriStar and this enabled Lockheed to concentrate on developing the range of its model, working with Engine manufacturer Rolls-Royce to bring greater thrust to provide transcontinental range and meet the requirements of other airlines. This proved successful in securing both Eastern and TWA as customers, signing letters of intent with both parties for almost 100 units on March 29 the same year to launch the project. At a combined $2.1 million, the commitment was then the largest ever for a ‘paper’ aircraft.

Construction of the first parts for the prototype airframe began on March 1, 1969 with assembly starting on June 24 the same year. The main fuselage sections were completed the following year and after the delivery of the first Rolls-Royce RB211 engines in June, the aircraft was structurally complete by the end of July and made public roll-out on September 1, 1970. After functional testing, engine runs and taxi tests the trijet, N1011 (c/n 1001) made its maiden flight from Lockheed’s Plamdale production facility in California, USA on November 16, 1970, just over eleven weeks later than its rival the DC-10.

Over the subsequent 16 months, five test aircraft completed 1,695 hours of flight testing to secure US Federal Aviation Administration (FAA) type certification for the airliner on April 15, 1972, slightly later than originally planned (British type certification followed in July 1972). The first production TriStar, N306EA (c/n 1007) was handed over to Eastern Airlines on April 6, 1972 entering service on April 26 between Miami and New York. TWA received its first, N31001 (c/n 1013) in early May, launching flights between St Louis and Los Angeles on June 25.

The initial production variant, the TriStar 1 had a range of 3,570 nautical miles (6,600km), enabling it to offer coast-to-coast flights in the US with a payload of 56,200lb (25,500kg). It provided seating for between 256 and 273 passengers in a two-class configuration, and from 330 to 400 in an all-Economy layout – the higher number coming from a high-density seating option for leisure routes. This was all on the main-deck with the galleys located below the main floor and accessed by a staff lift. Lockheed offered an optional lower-deck seating lounge connected to the main-deck by a stairway, but this was not selected by many customers.

The TriStar, like all other commercial production models of the time, was crewed by a team of three with the Flight Engineer responsible for the functioning of the aircraft’s systems. It was fitted with advanced avionics though, and was the first widebody to receive FAA certification for CAT-IIIC landings, Lockheed having worked on auto-land systems on the military C-141 and C-5 and the Jetstar executive jet. Linked to this was the Direct Lift Control system, which improved the approach characteristics of the jet under manual and automatic control (this deployed spoiler panels on the wings to maintain a smooth descent).

This marquee of the airliner sold better than the baseline DC-10-10, its nearest equivalent (163 units were sold to eleven customers). Lockheed’s initial decision to work on developing the TriStar’s range had meant that it had produced a very competitive aircraft. It may have arrived in the market later than the DC-10, but the extra time working on the design of the model meant that it could offer a number of performance improvements to its rival. The majority of these came from the 42,000lb (187kN) thrust RB211 powerplant, an engine that was advanced for its time, its three-spool design and carbon fibre fan offering better efficiency and power-to-weight ratio than any of its rivals. However, there were a number of problems developing the innovative engine, and at a time of high inflation and a downturn in the world economy it almost resulted in the closure of Lockheed and Rolls-Royce. The UK company actually went into receivership in early 1971, but was able to restart operations shortly after, as the British Government provided state subsidies on the condition the US government guarantee the bank loans Lockheed needed to complete the TriStar project.

Lockheed had been looking at extending the TriStar family from an early stage. The first development was the -50, which increased the aircraft’s gross weight from 430,000lb (195,000kg) to 450,000lb (205,000kg). This was made available to existing operators, but was never offered as a factory option.

The -100 variant followed in 1975, providing extra fuel capacity in larger wing and central fuselage tanks to further increase the take-off weight to 466,000lb (211,000kg). The -150 was also offered as a conversion to -1 operators, boosting the maximum take-off weight still further to 470,000lb (213,000kg). Only 13 -100s were delivered to Cathay Pacific Airways, Gulf Air, Saudia and TWA as it was found that the extra weight could cause major flight limitations on shorter runways, particularly during hot weather.

To overcome these problems the manufacturer developed the -200 in 1976, with up-rated 50,000lb (222kN) RB211-524B engines providing additional thrust. The first -200, HZ-AHD (c/n 1144), was delivered to Saudia on May 28, 1977 with the last, A4O-TT (c/n 1223), joining Gulf Air on December 2, 1981 – 24 were built in total, eight for British Airways, three for Gulf Air and 13 for Saudia. A further upgrade, the -250 was also offered using the RB211-524B4I engine to increase the maximum take-off weight to 510,000lb (231,000kg) and fuel capacity from 23,600 gal (89,335 l) to 31,632 gal (119,735 l). Only six aircraft, all operated by Delta Air Lines were upgraded to this configuration.

The final variant came in the form of the -500, launched by British Airways and first flown in October 1978. This long-range version featured a 13ft (4.3 m) shorter fuselage but with an increase in wingspan of 11ft (3.3m) to 164ft (50m). Powered by 48,000lb (222kN) thrust RB211-524s it was able to fly over distances of some 6,200 miles (9,975km), becoming an able replacement for B707s and DC-8s on long thin routes and to launch new intercontinental services.

Joint FAA and CAA certification of the -500 was issued in April 1979 and the first aircraft, G-BFCC (c/n 1164) was delivered to British Airways on April 29, entering service on the London/Heathrow – Abu Dhabi route on May 7. In total 50 -500s were delivered, many joining existing TriStar operators, although new customers were secured in the form of Air Lanka, Alia Royal Jordanian Airlines, BWIA West Indies Airways, Pan American World Airways and TAP Air Portugal.

As Lockheed entered the 1980s it became clear to the manufacturer that there were limited options for the TriStar. The more efficient ‘twins’ from Airbus and Boeing had limited the market for new sales, while a number of second-hand airframes were already available to airlines. The company acknowledged in the summer of 1981 that it would require at least 24 sales per year to make the programme viable, and with a declining orderbook and limited future sales leads, it decided to close the production line. The last two aircraft JY-AGI (c/n 1246) and JY-AGJ (c/n 1248) were delivered to Alia Royal Jordanian on June 3, 1985 at which time the TriStar programme was confounded to the history books.

Although the aircraft had been popular with airlines in the US it never secured the same demand in other global markets and only secured limited success around the rest of the world. There were some notable customers outside of the US though the most notable being Air Canada, All Nippon Airways and Cathay Pacific Airways. In Europe the largest user was British Airways, which at one point operated 23 of the type. In total, 250 TriStars were built, but only 249 were delivered as the prototype was retained by Lockheed.

As the 1980s continued more of the original TriStar operators were retiring the model, replacing them with more modern designs like the A300, A330 and B767. Although this resulted in new customers for the type, as additional aircraft entered the second-hand market, it meant that more were entering storage. With a large supply and only a small demand many of these never returned. Some examples were converted for cargo, VIP or military service but many were simply left to rot becoming little more than just a set of spare parts.

The table below highlights the declining operations of the TriStar over the past 30 years. According to OAG data from Schedules iNet, there were 241,153 departures planned to operate with the TriStar in 1981, a figure that rose to 254,405 in 1983, a milestone figure that was never subsequently exceeded. In fact since then there has only been a year-on-year growth in departures with the type on two occasions in the 25-year period.

With purchase and lease costs hitting the floor, the second-hand TriStars did become popular with ACMI and charter carriers during the 1990s. Canada’s Air Transat, Royal Airlines, Worldways all operated the type on leisure routes to the UK. Meanwhile, Air Atlanta, Peach Air and Air Ops of Sweden were just three of the European companies offering the aircraft to established carriers when additional capacity was required or if they suffered any technical problems with their own fleets. In fact many of the latter’s seven TriStars would sit idle at UK airports waiting for lucrative ACMI contracts.

As we entered the 21st Century only a small number of aircraft remained in service, some with the Royal Air Force and others flown by obscure charter companies in Africa and the Middle East with examples recently flying over the past five years on the Benin, Burkina Faso, Central African Republic, Chad, Equatorial Guinea, Kyrgyzstan, Liberia, Mali, Sao Tome & Principe and Sierra Leone aircraft registers.

The table below highlights the last five scheduled operators of the TriStar and their final routes, according to OAG’s Schedules iNet database:

As an aircraft that was popular with passengers and crews alike, the TriStar seems to have never fulfilled its potential. Lockheed had a target of 500 sales to breakeven, but only achieved half that level and despite its success with its propliners, the commercial jet market was a step too far for the manufacturer. The low sales level is strange given that the world’s TriStar fleet had one of the highest levels of achievement in terms of reliability and maintainability, with operators regularly reporting profits on the routes it served.

The table below highlights the largest scheduled operators of the TriStar over the past 30 years by planned flight departures: