The rivalry between the Boeing 737 and Airbus A320 is among the fiercest and most famous in aviation history. However, the 737, which is roughly 20 years older than the A320, originally competed with the McDonnell Douglas DC-9. As such, when the A320 first came out in the late 1980s, the battle became a three-way battle between it, the 737, and the DC-9 (then known as the MD-80), However, in the 1990s, McDonnell Douglas merged with Boeing, and the DC-9 came to an end.

The final DC-9 variant was the MD-95 (later rebranded as the Boeing 717), a smaller, lighter aircraft designed for regional routes that was most comparable to the 737-600 or A318-100. Before the MD-95, however, came the MD-90, a stretch of the MD-80 with updated engines to directly compete against the A320-200. Still, while over 4,700 A320-200s and over 4,900 737-800s (which came out after the MD-90) were sold, only 116 MD-90s were produced, and the MD-90 is no longer in service.

The McDonnell Douglas MD-90 In A Nutshell

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The McDonnell Douglas MD-90 is the third generation of the DC-9 family. Just like the rest of the series, the MD-90 is a T-tail narrowbody with rear-mounted engines and five seats per row in economy. Whereas the prior DC-9 and MD-80 came in multiple iterations, most MD-90s were produced as the base MD-90-30. Only two MD-90-30ERs were built, while 29 MD-90s were built with a full glass cockpit. Another two MD-90-30T ‘Trunkliner’ models were assembled in China.

The MD-90 was stretched compared to the MD-80, and at 152 feet seven inches (46.5 m), the aircraft is longer than an Airbus A321-200. However, because of its narrower fuselage, the MD-90’s passenger capacity is comparable to that of an A320-200. It featured the same cockpit as the MD-88, along with a variant of the IAE V2500 engine. This turbofan is more famous for being used on the A320 family, while the MD-80 was equipped with the Pratt & Whitney JT8D-200.

The MD-90 was a thorough update of the MD-80, but if you’ve never seen one, you wouldn’t be the first. Only 116 were ever built, and Delta Air Lines became the only operator of the MD-90 in the type’s final years. While the MD-90 took its place as a workhorse for the airline, Delta sunsetted the type in 2020 as a result of the COVID-19 pandemic. These were the last MD-90s flying for any airline worldwide, and they were retired alongside Delta’s MD-88 fleet.

Why Was The MD-90 So Rare?

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In large part, the MD-90 was extremely rare worldwide because Delta Air Lines purchased most examples. The MD-90 was ordered by over a dozen airlines, but in small numbers. This already made the economics of flying the MD-90 challenging, since maintaining parts for and retaining staff trained on a fleet of six or 12 aircraft results in high unit costs. In addition, the MD-90s also had maintenance challenges, and their IAE V2500 engines were expensive to maintain.

Delta Air Lines initially operated only 16 MD-90s, but it began to dramatically increase the size of its fleet in the early 2010s. Coming out of the Great Recession, the company could choose to buy new Boeing 737 or Airbus A320 family aircraft for growth, but these planes would be expensive. Used MD-90s, however, could be acquired for less, while having similar operating costs as an A320-200 or 737-800. Delta would eventually grow its operational MD-90 fleet to 65 units and purchase another 13 as parts donors.

While many airlines experienced maintenance problems with the MD-90, Delta’s TechOps was well-equipped and well-experienced to work on the MD-90. As the Atlanta-based carrier grew its fleet, so too did Delta TechOps grow its familiarity with the aircraft. While no other airline wanted them, Delta acquired as many as it could, and these planes were reliably used for a wide variety of domestic missions.

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Why Was The MD-90 Less Popular With Other Airlines?

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The MD-90 was unpopular more or less from the outset, regardless of Delta having acquired so many examples. This contrasted with its predecessor, the MD-80, which sold nearly 1,200 units, in large part due to being first on the market, as it had a seven-year head start on the similarly sized Boeing 737-400 and Airbus A320-200. However, with its Pratt & Whitney JT8D-200 engines, the MD-80 burned more fuel than either of the two.

The MD-90 was more efficient, but it kept the same wing as the MD-80. This greatly restricted its range and field performance, decreasing its versatility. This was further exacerbated by its relatively low fuel capacity. Despite entering service seven years later, the MD-90 had a comparable range to the 737-400, so, against the already in-service A320-200 and the upcoming 737-800, the MD-90 was outclassed. The MD-90 was also only available in one size, compared to several A320 and 737 variants.

The MD-90 was equipped with the IAE V2500-D5 turbofan, which was essentially the same engine as the V2500-A5 found on the Airbus A320 family but adapted for side mounting. However, the IAE V2500-D5 experienced significant reliability issues in its early years. Another point of pain for early MD-90 operators was that the electrical system was completely new, and this, too, was unreliable. As such, the MD-90 garnered a reputation for being a ‘hangar queen’ when it was first introduced.

How Did The Market Look When The MD-90 Came Out?

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While the McDonnell Douglas MD-90 was an inflexible aircraft, not every airline requires a plane with enough range to cross the United States. A market exists for a cheap, large aircraft to perform regional routes with superior fuel efficiency to older airliners. However, the MD-90 was being developed during the early 1990s, when the airline industry was in decline. The market was challenging, and airlines preferred models with greater capability, more optionality in sizes, and more modern technology.

The MD-90 was launched with 50 orders from Delta Air Lines and another 110 options. Delta originally intended to use the MD-90 to replace its Boeing 727 fleet, but the carrier underwent a major restructuring in the 1990s. Combined with the early reliability issues, Delta ended up taking only 16 examples out of its original order, with the rest cancelled.

As such, the program essentially lost its most important customer, and McDonnell Douglas, which was always more focused on its military division, was unwilling to invest in material improvements to the MD-90 program. Boeing merged with McDonnell Douglas in 1997. From its perspective, the main appeal of the merger was acquiring McDonnell Douglas’s lucrative military division, which included famed aircraft like the C-17 airlifter, the F-15 air superiority fighter, and the F/A-18 multirole fighter.

However, as for the commercial division, Boeing preferred to sell its own aircraft, so the MD-90 was killed in favor of focusing on the 737, while the MD-11 program was ended in favor of the 777. The in-development MD-95, smaller than any 737 variant, was rebranded as the 717, but this jet never found a real market either.

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How The MD-90 Was Used In Its Final Years

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Delta Air Lines was the launch customer for the MD-90, and it became the type’s last operator in the 2010s. The initial fleet of 16 examples was used heavily in Salt Lake City as well as Delta’s former hub in Dallas. After the company’s merger with Northwest Airlines, the MD-90 was used prominently in Minneapolis and Detroit, as the aircraft had enough range to reach the East and West coasts from these hubs.

Eventually, the MD-90 was also used on shorter routes from Atlanta alongside the MD-88, but it routinely operated longer flights than its older sibling. The MD-90 used the same pilot pool as the MD-88 due to cockpit commonality, and Delta configured it with 16 first class seats, 25 Comfort+ seats, and 117 economy seats. This is one additional seat compared to the A320-200, and two fewer than the carrier’s 737-800s. In economy, the MD-90 featured a 2-3 layout, identical to the Boeing 717.

The second-hand MD-90s were a cheap way to add capacity and upgauge following Delta’s retirement of the DC-9-50, but they were expensive to maintain on account of their IAE V2500-D5 engines. Aftermarket and overhaul support dried up in the late 2010s, and the MD-90s were not maintained in-house.

As such, Delta began retiring MD-90s in 2017, with the Airbus A321-200 serving as its replacement. The COVID-19 pandemic accelerated the type’s retirement schedule, and Delta operated the world’s last commercial MD-90 flight on June 2, 2020, from Houston to Atlanta.