One of the most storied lines of business aircraft began in the mid-1950s with something of a leap of faith—to invest in a modern turboprop-powered executive transport that would compete against the huge surplus of cheap, repurposed World War II-era airplanes that had been awkwardly pushed into that role.

After first considering a similar route, by adapting its amphibious, piston-engine Widgeon or C-1 Trader military hauler to the corporate role, Grumman Aircraft Engineering determined the best solution to meet the needs of an expanding base of corporate fliers lay in a fresh, low-wing design with a true stand-up cabin.

The company began work in 1956 on what would become the G-159, more popularly known as the Gulfstream I, with the first prototype flying in August 1958. Powered by dual Rolls-Royce RB.53 Dart turboprops and offering seating for as many as 24 passengers, the GI was designed with key input from early depositors who shelled out $10,000 apiece for production slots.

The result was a modern, speedy, and pressurized corporate aircraft that looked purpose-built to impress. Tall, retractable tricycle landing gear, necessary to clear the massive Rotol prop blades, ensured its ramp presence, while the smooth, clean wing offered impressive efficiency, range, and speed for the time.

Corporate customers responded, with 200 GIs built over the next decade for buyers as varied as Walt Disney, Ford Motor Company, and NASA. Grumman also explored a stretched version, dubbed the GI-C,  for regional airline use; only five were produced.

Nine TC-4C Academe variants were also built as trainers for the A-6 Intruder attack aircraft. That adaptation hinted at the GI’s talents as a multipurpose platform, which became clearer two decades after the last airframe left Grumman's Bethpage, New York production facility in 1969.

Now there are only about a half-dozen of the model still in service worldwide.

The Soul of a Warbird

Georgia-based Phoenix Air Group acquired its first GI in 1989, adding seven more over the next decade and another eight in 1999 when the company purchased aircraft and parts from a government-owned Venezuelan petroleum supplier.

"The GI is one of the most solid and reliable aircraft we've ever flown," said company senior v-p and COO Dent Thompson. That sturdy construction stemmed from Grumman's wartime experience, he added, down to rudder pedals with openings large enough for a pilot’s foot to pass through, allowing them to maintain yaw control even with a wounded leg.

"We'd also use that as our resting posture when flying," laughed Dave Greer, program manager for special missions operations. "Talk to any Gulfstream pilot today, and you'll see the scuff marks on their shoes."

That was just one legacy GI feature carried over to subsequent aircraft. The basic airframe configuration proved so robust that Grumman, and later Gulfstream Aerospace, continued with the same forward fuselage and cabin in the subsequent GII business jet and on through the G550 family.

Phoenix Air operated its GI fleet for more than 30 years in a wide variety of roles, from civil cargo and air ambulance operations to supporting government missions ranging from radar testing and electronic warfare and simulator training to more clandestine purposes.

For example, the company stood up a dedicated GI fleet out of Key West, Florida, in support of AeroMarti, an airborne radio (and later television) transmission platform that broadcast into Cuba until 2014. "We flew for at least six hours at a time, transmitting Major League Baseball, telenovelas, and certain... 'commercials,'" said Steve Christopher, vice president for military programs.

Ivan Betancourt, Phoenix Air's quality assurance manager for Gulfstream aircraft, noted the GI pioneered systems that would prove vital to the company decades later. "It was one of the first civil airplanes with an APU (auxiliary power unit), which was new technology in business aviation," he said. “We took advantage of that to generate the power needed for special missions equipment."

Fitting an entire broadcast studio into the GI's cavernous cabin did pose some issues, however. Even after stripping out interior panels and sound insulation, "the system was packed in the back [and] there just wasn't an air-conditioning system sufficient to dissipate that heat," Christopher said. "We flew high enough so the heat radiated through the skin."

Other missions saw the aircraft flying across the rugged terrain of South America. "We'd depart out of Guatemala City at night in the middle of thunderstorms," recalled pilot Henry Hiteshew. "The props would sometimes [throw ice] and hit the fuselage, and that's when you'd think about seeing your family again—but that airplane was a tank."

"I just loved working on the airplane," added Betancourt, who—like Hiteshew—came to Phoenix Air from the former Venezuelan operator. "The GI was not an easy or simple airplane by any means; it was complicated, but it gave me a lot of gratification to work on the airplane and then see it perform so well."

The aircraft also proved surprisingly reliable, even as OEM parts supplies dwindled. Phoenix Air implemented several procedures to keep the airplane flying, from mounting specialized equipment brackets to replacing welded control surface skins with riveted panels to facilitate corrosion repairs.

“We received an approval for those repairs and others through an AMOC (alternative means of compliance),” Christopher explained. "Grumman personnel simply never expected that GIs would be flying as long as they did, or ever thought their aircraft would be used like we used it.”

Years later, he continued, “we hosted one of the original GI engineers and we showed him around the airplanes and what we’d done to keep them flying. It was like his child had grown up. He was just so proud."

A Bittersweet Goodbye

Another point of pride came during a family day hosted by Gulfstream Aerospace to showcase its then-new G650 against the backdrop of its previous aircraft lines. Greer noted Phoenix Air sent a GI and GII business jet to Savannah, Georgia, for the event.

"They parked our GI next to a G650, and guess which line was longest?" he recalled. "People were lined up around the block to see inside the GI."

Even with its particular talents in special operations, the GI's tenure with Phoenix Air ended in October 2021, with newer and more efficient airframes assuming most of its missions. The company hosted a June 2022 luncheon celebrating the aircraft’s time in the fleet, its role in supporting Phoenix Air's operations, and its importance to corporate aviation.

"The mighty GI will live on in Phoenix Air memory," Thompson said.

"It was an awesome airplane," Christopher added. "Of course, today's modern turboprops come out ahead on maintenance and moneywise—those big, loud Darts suck a lot of gas—but even now I think it's hard to find a good, solid airplane that offers the same range, endurance, speed, and cargo capacity."

In fact, when asked if any one modern aircraft can fulfill the same breadth of missions as the GI, Christopher offered a blunt response. "The short answer is no."