MIAMI — The first flight of Boeing’s original 737 took place 50 years ago today, and Airways marks the anniversary by taking a look at the first unit ever built, and how it has contributed as a testbed to implement innovations in today’s commercial aviation.

The “Baby Boeing” is born

At the time Boeing announced the creation of its third jet airliner program in 1965, the company had already successfully delivered two multi-engined jets — the 707, with four engines, and the 727, with three engines. But the newest plane, dubbed the 737, looked like a miniature version of its 707 predecessor, and thus ended up with the nickname “The Baby Boeing.”

The original concept called for seating of only 50-60 passengers, equivalent to many of today’s “regional jets.” however, launch customer Lufthansa required Boeing to stretch it to seat 100. Next, United came along and placed an order for forty 737s, but they too wanted Boeing to stretch the plane. Three feet were added to the length, and thus the second variant was born and became the 737-200.

Though it was first rolled out of the factory in September, 1966, this prototype aircraft was introduced to the world on January 17, 1967 at Boeing’s “Thompson Site” located at Boeing Field. It was christened by uniformed flight attendants from the seventeen airlines who had placed 737 orders at the time.

The assembly building at Plant 2 wasn’t tall enough for the 737’s vertical stabilizer, so it had to be attached by crane in the plant’s parking lot, then rolled down to the Thompson Site (where 392 additional 737s were built). This tail attachment process continued for the first eight 737s built.

The first plane was serial number 19437, registered N73700 and internally known as PA-099. It performed high-speed taxi tests at Boeing Field on April 8, 1967, and made its first flight with Brien Wygle and Lew Wallick at the controls at 1:15PM the following day. Boeing’s president at the time, Bill Allen, told reporters after the flight, “We’ll still be building this plane when I’m in an old-man’s home.” He passed away in 1985, and the 737 legacy continues.

During the flight, Wygle said over the radio, “I hate to quit… this airplane is a delight to fly.”

At the time the 737 came to market, two other players were already on the field, the BAC 111, and the Douglas DC-9, so people within the industry questioned the 737’s ability to succeed. The 737-100 design schematics measured the plane at only 94 feet long, with a 93 foot wingspan, leading some to call it “The Square Plane” or “Fat Albert.” Once the -200 received its stretch, it measured 96 feet, eleven inches long, with the same 94-foot wingspan.

Boeing designed the plane with six-abreast seating, which gave them a selling point over rival DC-9’s five-abreast seating. Another advantage of the 737 was its wing-mounted engines. They provided a more balanced center of gravity, and made engine maintenance possible by standing on the ground, versus up on a ladder for tail-mounted DC-9 or 727 engines.

N73700 never flew for an airline, though at one time it was painted in Lufthansa’s livery. Boeing historian Michael Lombardi helped Airways piece together the aircraft’s history with Boeing. Both early models received their type certification on December 15, 1967. Throughout 1968, N73700 toured North and South America.

In February 1969, Boeing began offering a gravel kit on the 737 so it could operate from unpaved runways in remote locations. N73700 was used to test this kit, which included a deflection ski behind the nose gear, an oversized main gear, protective shields over the hydraulic tubing and brake cables on the main gears.

The bottom of the onboard flaps were reinforced with fiberglass. The underside of the wings and fuselage was painted with teflon-based paint. The underside of the engine nacelles was fit with anti-vortex jets, which disrupted the vortices that could potentially ingest gravel.

In 1972, N73700 toured Australia that March then performed further gravel testing in Peru that June. In August of that year, it performed grass field testing in Hope, British Columbia, about 100 miles NNE of Seattle.

From N73700 to N515NA

N73700 completed its career with Boeing in May 1973, with a tour to the Far East, and was delivered to NASA on June 12th of that year.

NASA used the plane as a Transportation Systems Research Vehicle, based at Langley, Virginia. The museum’s website also notes the plane is still on loan from NASA, which gives one the impression that it could potentially return to the skies one day. It may also explain why it hasn’t been restored to its original rollout livery.

The plane has two cockpits! One is located where the standard cockpit would be, in the nose of the plane. The second is placed where First Class would normally be located. Inside the second cockpit, it looks like the hideous love child of an Airbus and Boeing, with glass displays but side stick controls rather than the center yoke common to Boeing jets.

Once with NASA, most of the flying of the plane was done from the back cockpit. Pilots did sit up front, acting as safety pilots.

Among the aeronautic achievements accomplished at NASA by using this airborne testbed are electronic flight displays. In 1974 and 1975, the plane was used to test the cathode ray tube electronic attitude indicators and horizontal situation displays which were implemented into Boeing’s 757 and 767.

From 1977 to 1978, NASA 515 was used to fly tests for the FAA, evaluating Microwave Landing Systems (MLS) performance. MLS ended up being adopted as the international standard approach and landing guidance system until GPS-based approaches became the standard.

Between 1978 and 1980, the plane tested landing technologies such as precision flare control, which improved touchdown accuracy and reduced aircraft time on the runway after landing. During the same time period, a profiled descent program was also tested, in which planes descended for landing by using automation, which increased fuel savings while decreasing the time it takes for a plane to descend to land.

In 1980 and 1981, laminar flow technology was tested in partnership with Boeing, using advanced paints on the wing surfaces. Laminar flow essentially creates a smoother flow of air over an aircraft surface, which reduces drag. The tests led to drag reductions for airliners. Today Boeing uses laminar flow on things such as the 787 Dreamliner engine nacelles, and the 737-MAX AT Winglet.

NASA helped modernize avionics by testing Digital Autonomous Terminal Access Communications (DATAC) on the plane from 1983 to 1988. In the joint program with Boeing, the team developed, flight tested and demonstrated practical use of onboard computer network to communicate between aircraft electronic flight systems. The NASA/Boeing DATAC system was adopted as industry standard.

In 1984-85, the plane conducted tests to improve and predict aircraft ground handling performance on slippery runways during bad weather. Technology was used by FAA, and the results were adopted for use at most commercial airports worldwide. Treacherous runways caused by inclement weather have been the source or contributor to many runway excursions, leaving to the loss of life and aircraft.

From 1985 to 1992, another Boeing program used the plane, to validate new computations to improve aircraft fuel efficiency during the climb and descent portions of flight. The program was called Total Energy Control System (TECS). The technology was applied on Boeing’s “Condor,” a remotely piloted vehicle built by Boeing for the Department of Defense.

McDonnell Douglas tested their Takeoff Performance Monitoring System (TOPMS) on the plane between 1985-1991. Display formats, computations, and alerts developed and demonstrated to improve information available to crew for assessing aircraft takeoff performance.

In 1989 and 1990, NASA 515 conducted flight tests to evaluate benefits of using electronic data link vs. voice as primary communications system between aircraft and air traffic control. The results were used in developing government-industry design and operational standards. The program’s technology has been adopted for use in newer Boeing 747 and all Boeing 777 cockpits.

Also in 1989 and 1990, NASA 515 was used in partnership with Honeywell to assess GPS (Global Positioning Satellite) performance for self-sufficient landing guidance system for proposed reusable spacecraft and for commercial aircraft applications. Technology used by Honeywell to improve airplane GPS systems is now in commercial use. The plane completed the first GPS-guided autoland of a full-sized transport in the United States.

From 1990 to 1993, the plane was used to help develop and test commercial wind shear sensors. NASA says that fifty percent of aviation fatalities from 1975 to 1985 were related to wind shear. The most notable case being Delta 191, which crashed on final approach during a thunderstorm at DFW Airport on August 2, 1985. As a result of the testing program, five wind shear measurement technologies were implemented, and became the standard for industry wind shear measurement.

NASA added two thousand flight hours to Number 515 from 1974 to 1994, and its service to the aviation industry cannot be overstated. One NASA scientist in particular, Lane Wallace noted frustration in how new ideas face a human and organizational tendency to resist change, and as companies grow in size, effectively communicating information about new innovations to all the necessary players becomes more difficult.

NASA 515’s final research flight was on June 27, 1997, as noted by a plaque in the forward cabin. It was maintained at Moses Lake, Washington, until September 21, 2003, when it was flown to Boeing Field where it has remained. It remains in NASA’s livery, and the Museum of Flight website says the plane is officially “on loan” from NASA. It would take a bit of work to get her back in the skies, but the plane has less than 4,000 hours on its airframe. Most commercial jets are flown past 60-65,000 hours.

Only thirty Boeing 737-100s were delivered to airlines. Interestingly, the first 737-100 was delivered to Lufthansa on December 28, 1967 — and the very first 737-200 was delivered to United the very next day. Of the seventeen original 737 customers, only Lufthansa and United are still in business. Lufthansa retired their final Boeing 737 on October 31st, 2016.

Boeing has said their current delivery timeline for the MAX-8 is mid-2017 but could be as early as this month. Launch Customer Southwest Airlines has announced they will not begin MAX service until October first, allowing Malindo Air to overtake the honor of being the first airline to have the MAX in service.

By the time Boeing does deliver the first 737-MAX, 737s will have been in production for fifty years — giving it the longest and most successful production run of any commercial aircraft ever built. Not including the BBJ series, Boeing has produced 30 737-100s, 1,114 737-200s, 1,113 737-300s, 486 737-400s, 389 737-500s, 69 737-600s, 1,156 737-700s, 4,469 737-800s and 475 737-900s.

The current order book for the MAX series stands at 3,703 (as of March 31, 2017), which puts the 737 past the previous record holder for the most-produced airliner, the Douglas DC-3 — though technically, most of those built were the C-47 Skytrain version, which was a WWII troop hauler. Many C-47s were reconfigured for airline service after the war.

Only 607 copies of the DC-3 were built specifically for civil use. A deal signed March 18th for 30 MAX placed by Iran’s Aseman Airlines is not yet reflected on Boeing’s Orders and Deliveries site.

Check out our photo gallery of the cabin: