6.6 The Jet Age Disruption?

Marcos Antonio de Lima Filho, PhD.

According to Christensen, the jet engine was not a disruptive innovation. Previous innovation scholars, many of whom have paved the way for disruptive innovation research, disagree about that. For them, the jet engine was:

• A technological discontinuity, built from “an entirely new and different knowledge base” (Foster, 1986, p. 36);

• A competence-destroying technology, and a major breakthrough (Tushman & Anderson, 1986);

• An architectural innovation (Henderson & Clark, 1990);

• A new dominant design (Anderson & Tushman, 1990).

In comparison, Christensen considered the jet engine as a technologically innovative, but not a disruptive innovation (Govindarajan & Kopalle, 2006). The jet engine was “a radical but sustaining innovation relative to the piston aircraft engine” (Christensen & Raynor, 2003, p. 69). Christensen does not deny the innovativeness of the jet engine. The problem here is his categorisation of sustaining vs. disruptive innovation, and the failure of his model to explain the market changes that unfolded:

When initially introduced, disruptive innovations are inferior to incumbent products on accepted performance dimensions, but they offer a novel mix of attributes that appeals to fringe customer groups, notably those near the bottom of the market (Christensen et al., 2018).

The jet engine outperformed the piston engine on all performance metrics. Due to their superiority and high cost, manufacturers introduced the first jets in high-end market segments. The industry incumbents succeeded with a disruptive strategy (Rolls-Royce and Pratt & Whitney) despite the theory’s prediction that it would fail. Other incumbents tried to stay with piston engines. According to Christensen’s model of disruption, incumbents should succeed with sustaining innovations; however, incumbents were rapidly displaced in this case. Within a decade, the majority of the market had switched from piston engines to jet engines (see Figure 6.6.1). “General Electric was an entrant in the jet revolution, and became very successful” (Christensen & Raynor, 2003, p. 69). GE entered late, in 1971, with the first high-bypass turbofan engine. This further contradicts the theory because entrants are supposed to succeed with a “sustaining innovation” strategy rather than a disruptive one. “These are anomalies that the theory of disruption cannot explain” (Christensen & Raynor, 2003, p. 69).

In my view, framing the jet engine as a “sustaining innovation” is an oversimplification, considering the significant technical and commercial obstacles it encountered during its introduction. Both established companies and newcomers faced unparalleled challenges at this time. Traditional aircraft manufacturers led the list of money losers among the Forture 500 Industrial for three consecutive years: Douglas in 1959, Lockheed in 1960, and General Dynamics in 1961 (Pattillo, 2001, p. 205).

Newcomers faced even greater hurdles, contenting with not only technical complexities but also the commercial viability of jetliner operations. As pioneers of jet engine technology, the British were keen to capitalise on its superiority over piston engines. Supported by government funding, de Havilland developed the Comet 1, an aircraft with a pressurised cabin that enabled operation at higher altitudes, avoiding turbulent weather and ensuring passenger comfort (Pandey, 2010). The Comet, as the world’s first jet airliner, flew at nearly twice the speed and altitude of its propeller-driven predecessors (Verhovek, 2010). However, the programme faced significant setbacks due to a series of accidents (Eden, 2015). The Comet 1 was plagued by metal fatigue, which caused catastrophic structural failures, ultimately undermining its success.

The operating economics of early jet engines made it difficult to justify rushing ahead with development, as airlines prioritised financial considerations over military concerns (Pattillo, 2001). Reportedly, major airlines like United and American Airlines informed Douglas Aircraft that the market was not prepared for jet engines (Pandey, 2010). Ralph Damon, the president of Trans World Airlines (TWA), argued that the economic benefits of a $1.5 million propeller-driven aircraft, such as the Constellation, outweighed the advantages of a $4 million jet offered by Boeing, despite the latter providing faster and less turbulent travel for passengers. In Damon’s words, “The only thing wrong with the jet planes of today is that they won’t make any money” (Verhovek, 2010).

After observing the British failure, leading US aircraft manufacturers – McDonnell Company, Douglas Aircraft, and Lockheed – decided to temporarily halt their plans for commercial jet planes, focusing instead on propeller-driven aircraft (Foster, 1986). At the time, Douglas was “resting on its laurels”. The company had just launched the four-engine, piston-powered, propeller-driven DC-7 and underestimated the looming threat posed by jet engines (Pandey, 2010). This sustaining strategy likely contributed to delaying Douglas’ entry into the Jet Era, ultimately leading to its displacement from a leadership position. While disruption theory suggests that incumbents generally succeed with sustaining strategies, this case seems to be another exception. The reluctance to embrace the disruptive potential of jet engines resulted in Douglas and other incumbents falling behind during the Jet Era.

Despite initial resistance, jet engines proved to be highly disruptive in both technological and commercial aspects, exemplifying Schumpeter’s concept of Creative Destruction. However, Christensen’s theory of disruptive innovation offers little to no explanation for this technological transition. The jet engine was, in his words, “a radical but sustaining innovation relative to the piston aircraft engine” (Christensen & Raynor, 2003, p. 69). This raises the question: “What exactly constitutes sustaining innovations?”

In contrast to Christensen’s strict definition of disruptive innovation (as outlined in Figure 2.8.2), sustaining innovation is vaguely defined. Sustaining innovations can be either revolutionary or incremental:

Radical sustaining innovations are at the complex end of the continuum. These “great leaps forward” tend to be complicated, interdependent, and expensive. Two classic examples of radical sustaining innovations are the systemwide upgrade of the telecommunications network from analog to digital technology and the move from black-and-white to colour televisions. Incremental sustaining innovations tend to influence an industry less dramatically (Christensen et al., 2004, p. 10).

There are many ways to categorise sustaining innovations (Christensen et al., 2004, p. 24). In a footnote, Christensen suggests using Henderson and Clark’s (1990) framework for defining innovation. From this classification scheme, sustaining innovations can be categorised into radical, modular, architectural, and incremental innovations (Christensen et al., 2004, p. 24). In conclusion, whereas disruptive innovation “is a specific type of technological change, which operates through a specific mechanism, and has specific consequences” (Danneels, 2004), sustaining innovation seems to encompass everything else.

The categorisation of jet engines as sustaining innovations stands in contrast to the viewpoints of early innovation scholars, who considered the Jet Age as a profound disruption in the aviation industry. These scholars argued that the jet engine represented “an entirely new and different knowledge base” (Foster, 1986, p. 36) and “a competence-destroying technology and a major breakthrough” (Tushman & Anderson, 1986). They explained it as “an architectural innovation” (Henderson & Clark, 1990) and “a new dominant design” (Anderson & Tushman, 1990). These scholars believed that the jet engine marked a radical departure from the piston engine, ushering in a new era of technological advancements that fundamentally transformed aviation.

These early innovation scholars drew extensively from the works of William J. Abernathy, whose significant contributions shaped their understanding of industrial evolution. Abernathy was among the pioneering scholars to differentiate incremental innovation from radical or disruptive innovations (Abernathy & Utterback, 1978; Abernathy & Clark, 1985). They were insightful in recognising that innovation is not a unified phenomenon: “some innovations disrupt, destroy, and make obsolete established competence; others refine and improve” (Abernathy & Clark, 1985). In his works, Abernathy recognised the jet engine as an “innovation that disrupts and renders established technical and production competence obsolete” (Abernathy & Clark, 1985). Empirical data supports this view, as jet airliners replaced piston airliners in less than a decade, relegating this old technology to obsolescence (Figure 6.6.1).

The Jet Age disruption was accelerated by the inherent limitations of piston-engine technology. Propellers were already encountering supersonic tip-speeds that destroyed their efficiency, and engines had grown so complex that additional horsepower depended on a large number of cylinders and complex supercharging (Crouch et al., 2020). This large number of moving parts generated problems in operation and maintenance.

Consequently, in numerous aspects, the jet engine represented a radical departure from the piston engine. Rather than building upon and reinforcing the applicability of existing knowledge, the Jet Age required the development of a new knowledge base. There are fundamental differences that separate piston engine technology from jet engine technology. The first is based on reciprocating pistons and cylinders, akin to the engines found in most automobiles. In contrast, turbojet and turbofan engines generate thrust by increasing the velocity of air flowing through the engine (Federal Aviation Administration, 2016, p. 6-13). Thus, jets and piston engines were built upon different scientific and technological foundations. While further incremental innovation in piston engines may indeed result in enhanced performance and efficiency, such advancements are insufficient to transform a piston engine into a jet engine.

Initially, Christensen adhered to the research tradition established by earlier innovation scholars, including Abernathy. In his doctoral thesis, he examined the history of the hard disk drive industry, expressing his aspiration to “follow in the steps of the late Professor William Abernathy” (Christensen, 1992a, p. 5). Furthermore, Christensen received the 1991 William Abernathy Award for the best paper in the management of technology (Christensen, 1992b). His early research papers frequently cited Abernathy’s work (e.g., Rosenbloom & Christensen, 1994; Christensen & Rosenbloom, 1995; Christensen, 1997), suggesting an awareness and appreciation of Abernathy’s contributions to the field.

However, with the publication of The Innovator’s Dilemma in 1997, Christensen redefined the concept of disruptive innovation, departing from the established research tradition without providing explicit justification for this shift (Section 6.2 - 6.2 Issues with Disruption Theory). In his new framework, the Jet Age ceased to be viewed as a classic example of profound disruption and creative destruction, as it had been in the works of earlier scholars. Instead, the jet engine was downgraded to the category of sustaining innovation, which occupies a marginal role in Christensen's theory.

In conclusion, the Jet Age epitomises a highly disruptive transition, one that challenges Christensen’s conceptualisation of such phenomena. The swift adoption of jet engines and the consequent displacement of piston engines highlight the limitations of Christensen’s disruption theory in accounting for instances of creative destruction on this scale. The Jet Age presents several anomalies to disruption theory, including incumbents failing due to adherence to sustaining strategies and entrants succeeding with disruptive approaches. Christensen himself acknowledges these inconsistencies: “These are anomalies that the theory of disruption cannot explain” (Christensen & Raynor, 2003, p. 69). The incongruity between the dominant disruption paradigm and the empirical observations from the Jet Age underscores the necessity for a more comprehensive definition of disruption.