In May 1949, U.S. Air Force Air Materiel Command issued Boeing a contract for the flying boom, to be installed in KB-29Ps. The system featured a flow pump capable of transferring fuel at the rate of 700 gallons per minute. SAC made it mandatory for all its new aircraft to be fitted with receptacles to accommodate the new equipment, but Tactical Air Command (TAC) continued to order fighters equipped with probes. Eventually a detachable hose and drogue was developed that could be added onto the flying boom, allowing tankers to refuel a wide variety of thirsty planes.

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The KB-29 and KB-50 were soon outdated, however, since the prop-driven tankers lacked sufficient speed to easily refuel jets. Although some KB-50s eventually mounted auxiliary General Electric J-47 en­gines to increase their speed, their active service days were numbered.

The next generation of dedicated tankers was developed in tandem with the new medium-range bomber that would become the centerpiece of SAC strength for more than a decade: the Boeing B-47 Stratojet. The B-47’s range, heavy payload and fuel requirements meant that IFR would be more important than ever. In response Boeing developed the KC-97 Stratotanker, an adaptation of the four-engine, prop-driven C-97 Stratofreighter. Both planes began their service life late in 1950 in training missions with the 306th Bombardment Wing. The Air Force ordered far more KC-97 tankers (Boeing produced 816 in all) than C-97 transports. Still, the piston-engine KC-97 needed to make a shallow dive to gain sufficient speed to refuel the B-47, which had to fly nose-up throughout the process. The introduction of the KC-97L, with a supplemental jet en­gine mounted under each wing, gave the tanker the speed required to refuel jet bombers without descending.

The Korean War saw the first tactical use of in-flight fueling for recon and fighter-bomber operations. In July 1951, a KB-29M re­fueled four Lockheed F-80s over North Korea—the first IFR over enemy territory. The first combat aerial refueling took place on May 29, 1952, during a bombing mission by 12 Republic F-84E Thund­er­jets from Japan, targeting Sariwon, North Korea. And that Sep­tember Lt. Col. Harry W. Dorris, flying an F-80 with a 265-gallon fuel tank on each wingtip, pushed the endurance envelope for pilot and aircraft during one marathon mission: He bombed, launched rocket attacks, strafed and did reconnaissance over the course of a sortie that lasted 14 hours and 15 minutes—refueling three times before landing.

Following the Korean War, the Hungarian and Suez Canal crises prompted continuation of training exercises and rotations begun earlier in the 1950s, when SAC transferred bomber and fighter wings en masse to forward locations. Many of those transfers involved IFR.

Meanwhile, U.S. Navy refueling shifted from the experimental to the operational phase, still relying on the probe-and-drogue method. Navy and Marine Corps aircraft continue to use this method today.

Though it served the B-47 and subsonic jet wings well, the KC-97 was ultimately destined to be replaced once the next-generation bomber, the Boeing B-52 Stratofortress, arrived. The reason? The B-52 had to cruise at near stall speed when refueling from the KC-97. Furthermore, the KC-97 could offload only 53,000 pounds of fuel, 21 percent of the B-52’s capacity, and the bomber burned a great deal of fuel descending to and climbing back from the KC-97’s altitude.

The B-52’s introduction led to the development of the most versatile tanker ever built—Boeing’s KC-135, which became the mainstay of the Air Force refueling fleet and still remains in service. Realizing that the Air Force would need a jet-powered tanker to complement its jet bombers, Boeing had begun work on the 367-80 prototype in 1952. The sweptwing 367-80—better known as the “Dash-80”—would be­come the first American-manufactured commercial jetliner, the 707/720 series, but it also yielded cargo and specialized use aircraft for the military. The KC-135A, featuring four of the new Pratt & Whitney J-57 engines and equipped with a flying boom, first flew on August 31, 1956. It carried 31,200 gallons of fuel, a tremendous improvement over the KC-97’s capacity of 8,513 gallons. Additionally, refueling could take place at 35,000 feet, almost twice the altitude of the KC-97. With a jet-powered tanker, bombers no longer had to slow down and decrease al­titude to take on fuel.

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