Home » Boeing Keeps Stretching the 737. Here’s Why That’s a Big Problem.

Boeing Keeps Stretching the 737. Here’s Why That’s a Big Problem.

Why was the emergency door that blew out of the Alaska Airlines Boeing 737 MAX-9 there if not needed? The answer to that question reveals how far some airlines will go to pack a cabin to its limits—and how far Boeing is willing to go to accommodate them.

The MAX-9 is the largest (so far) of the 737 MAX series. At maximum permissible coach density it can have 220 seats. The Alaskan version has 188 seats: 16 in First, 24 in premium and 138 in coach. That difference meant that the emergency exit at row 26 was not required to provide additional emergency evacuation of the cabin in the case of a crash. Hence it was “plugged”—supposedly locked securely in place. Except that it wasn’t, as investigators have already discovered, along with numerous other manufacturing defects on other MAX-9 jets.

Behind this event is the amazing story of the little airplane that suddenly began to get a lot larger. As each model of the 737 has appeared the cabins have become longer and longer… and longer.

When the 737 was conceived in the 1960s its fuselage length was 100 feet. It was promoted to the airlines as a new “baby” airplane to provide transforming jet speed service on short domestic routes that until then had been served by far slower propeller-powered airplanes. It had compact dimensions—it was described as “100 square” because its wingspan was roughly the same as its length and it had 100 seats in the cabin.

Today the largest of the 737 MAX series, the MAX-10, has a fuselage that is 143 feet long, designed to take maximum seating of 230. The MAX-10 is not yet flying with airlines (it won’t be at any gate before next year) because its certification process has been long delayed by changes required by U.S. and European regulators after the two deadly crashes that caused the world fleet of 737 MAX jets to be grounded for twenty months. Those changes mostly involve its flight control software, and do not reflect the extraordinary density of its all-coach cabin.

In fact, nothing better illustrates the efforts Boeing has made to keep the 737 competitive so many decades after it was conceived than this step-by-step stretching of the fuselage’s length. “Stretch” is the technical term used, achieved by adding new sections of the fuselage, both ahead of the wings and behind them.

And this is why the jet has remained so popular with airlines, particularly budget carriers across the world. It is cheaper to buy than its Airbus competitor and its utility is legendary—after a breakthrough upgrade with a third generation with new engines in the mid-1980s it became the world’s workhorse. By last year, more than 11,000 had been delivered, at that point having made around 84 million flights.

The MAX-10 is the absolute limit of what is possible in passenger capacity for the 737. But it’s unlikely that the 230-seat density will ever appear in the U.S. and will first be used by budget carriers in Asia. The optical effect of a cabin that long that doesn’t get any wider (the width is 11 feet 6 inches) is to increase the impression of a tunnel, and although the cabins feature clever lighting and bright colors the visceral impact is unavoidably claustrophobic. What are the safety implications for jamming so many seats into the cabin?

The near-miraculous evacuation of nearly 400 people from a Japan Airlines jet that collided on a Tokyo runway with a Coast Guard airplane demonstrates how advanced the technology has become for big jets—this was an Airbus A350, with two aisles and easily-accessed exit doors. Getting as many as 230 people out of a long and narrow single-aisle jet would be a far more demanding test of the cabin crew and the airplane’s layout.

In 2017 a Daily Beast investigation found that the obligatory tests carried out in the U.S. on every new jet to ensure that all passengers can safely exit a cabin in an emergency do not reflect how densely packed coach class seating has become. I examined more than 900 pages of Department of Transportation documents and FAA regulations that address the way airplane cabins are configured to ensure effective emergency evacuation. All of the tests were devised decades before the appearance of budget airlines, not to mention the expanding girth of many Americans.

At that point I specifically asked for details of the emergency tests carried out for the new MAX series jets, including the MAX-10. Neither the FAA nor Boeing would release the details of the tests that had been carried out, citing the reason as “the proprietary nature of the data.”

However, Boeing did tell The Daily Beast: “The public can be assured that Boeing substantiates the evacuation capability of our airplanes using the maximum allowable number of passengers, which is significantly higher than what airlines typically use in their operations.”

An FAA spokesman explained that airlines themselves test emergency evacuation procedures using a “partial demonstration” in which only a section of the cabin is used with typical seating—if the airplane manufacturer has already carried out the full-scale tests. Boeing’s spokesperson said, “the FAA may, in certain circumstances, allow the evacuation capability of the airplane to be substantiated by a combination of testing and analysis.”

Experts I spoke to at the time said there was no doubt that the evacuation testing met the standards set for them, but that the issue, as yet to be tested in real life, was were those standards rigorous enough for the age of ultra high-density seating?

The idea that the 737 would turn out to be Boeing’s greatest cash cow would have seemed preposterous when it was launched. The project was rushed and plagued with problems.

Boeing had ushered in the jet age with its brilliant intercontinental jet, the 707. The company’s priorities were to keep its world dominance in larger jets, and to recoup the huge expenses of its pioneering work. The commercial airplane division was, in fact, subsidized by the military division, where an Air Force jet was used as the prototype for the concept of the 707.

The 737 was an untypically urgent response by Boeing to its main U.S. competitor, Douglas, who had produced a small jet, the DC-9, spotting a gap that Boeing had missed. The DC-9 cabin had five-abreast seating – 3/2. The Boeing designers replicated the dimensions of the 707’s cabin to allow 3/3 seating. However, the first model of the 737 so seriously failed to meet Boeing’s performance claims that the launch customer, Lufthansa of Germany, said it represented a serious lapse in what until then they had regarded as Boeing’s exemplary engineering—although one of the main problems was the performance of the engines, made by Pratt & Whitney.

Now, after such a long run and faced with yet another crisis with the MAX series, the question is, was this a stretch too far?


January 2024