The most ambitious naval aviation concept the United States ever fielded was not the nuclear-powered supercarrier. It was a 785-foot helium airship with an interior hangar bay full of biplane fighters that could be launched and recovered in flight. There were two of them: the USS Akron, commissioned 1931, and the USS Macon, commissioned 1933. Together they constituted the world’s only fleet of operational flying aircraft carriers. Both were lost within four years of each other. The U.S. Navy never tried it again.

And yet — for a brief window in the early 1930s — these enormous machines really worked. They flew across the Pacific, launched and recovered F9C Sparrowhawk fighters via a trapeze mechanism inside the airship hangar, and demonstrated a scouting concept that, on paper, would have given the U.S. Pacific Fleet eyes over a sea area no surface ship could match. The story of why it stopped working — and why no air force has tried it seriously since — is one of the most fascinating “what ifs” in naval aviation history.

The Skyhook trick

The technical marvel that made the Akron and Macon real aircraft carriers — rather than aerial curiosities with mascots — was the trapeze recovery system. Each airship had an internal hangar bay accessed by a T-shaped opening in the lower hull. Inside the hangar, a steel trapeze hung from rails. Aircraft could be lowered on the trapeze, started up, and released into the slipstream. To recover, the pilot of an F9C Sparrowhawk would fly up beneath the airship, match its speed (around 70 knots), and engage a hook mounted above his upper wing onto the cross-bar of the lowered trapeze. The trapeze would then haul the aircraft up into the hangar bay, where the wings could be folded for storage.

It sounds impossible. It worked. Trained Sparrowhawk pilots eventually got the recovery to the point where they could trap on the trapeze in moderately rough air with the airship pitching and yawing. Each Macon Sparrowhawk pilot averaged dozens of successful recoveries. Lt Comdr Frederick “Trapeze” Trapnell of the Macon perfected a recovery technique that involved a precisely-timed flare from below — the same conceptual approach modern carrier pilots use to time the final descent onto the deck.

The Akron disaster

USS Akron was lost on the early morning of 4 April 1933, off the New Jersey coast, in a violent thunderstorm. Caught in a powerful downdraft, the airship was forced into the Atlantic before her crew could recover. 73 of the 76 crew members aboard died, including Rear Admiral William Moffett — the founding father of U.S. naval aviation and the Akron’s most prominent champion. The loss made the Akron disaster the deadliest aviation accident in history at that time, surpassing the loss of the British R101 two years earlier.

The investigation pinned the cause on a combination of bad weather forecasting, the airship’s tendency to descend rapidly when caught in cold downdrafts, and inadequate altimetry that meant the crew did not realise they were within 1,000 feet of the sea until far too late. Several proposed structural improvements were applied to the Macon, but the deeper problem — that rigid airships were uniquely vulnerable to localised weather — was never going to be solved by engineering.

“The airship will, in my opinion, ultimately rank with the surface battleship as one of the great vehicles of national defence. The scouting range it offers is unmatched by any other naval platform. We must continue to develop this capability.”

Rear Admiral William Moffett — Chief of the U.S. Navy Bureau of Aeronautics; lost aboard USS Akron, 4 April 1933 (statement, 1931)

The Macon disaster

USS Macon outlived her sister by less than two years. On 12 February 1935, returning to her base at Sunnyvale (now Moffett Federal Airfield) after fleet exercises, she ran into rough weather off Point Sur on the central California coast. The upper vertical tail fin failed — Macon had a known structural weakness in the rear ring frame that had been identified and was scheduled for repair — and the tail loss punctured three of the aft helium gas cells. With the rear of the airship losing lift rapidly, the captain ordered full power and ballast release. The airship climbed in a pitched-up attitude, ventilating helium uncontrollably through the safety valves as it passed pressure altitude. By the time the engines could no longer hold her up, she was over the ocean. She settled tail-first into the Pacific.

74 of 76 crew survived. The airship sank to 1,500 feet of water, taking four Sparrowhawks with her. The wreck was rediscovered in 1990 by a Monterey Bay Aquarium Research Institute expedition. Sport-diver and museum surveys since have documented an extraordinary state of preservation — the wooden Sparrowhawk cockpits are partially intact, complete with instrument panels and seat frames recognisable to any 1930s aviation historian.

Why nobody tried it again

Several reasons combine to explain why the airborne aircraft carrier concept died in 1935 and has never been seriously revived. First, the loss-of-life statistics were unmistakable. Two airships had cost 75 lives in 22 months. No fleet commander wanted a third one. Second, the technological frontier was moving away from helium-lift airships toward winged aircraft with constantly improving performance. By 1937 (the Hindenburg disaster), even commercial passenger airships were finished as a concept.

Third — and this is the part that aviation historians still debate — the actual operational utility of the flying carrier was unproven. The Sparrowhawks the Macon carried were not particularly capable scouts. The 70-knot airship could not run from any modern interceptor. And the cost-per-mission of operating one of these enormous vehicles was probably comparable to that of a small surface carrier task force, without the firepower or staying power.

The concept has reappeared occasionally — Lockheed’s 1970s CL-1201 airship-carrier study, various drone-carrier proposals using converted transport aircraft, and most recently DARPA’s “Gremlins” programme to launch and recover small UAS from a C-130 — but the rigid-airship-as-mothership has remained firmly in the museum era. The Akron and Macon are the only two such ships ever fielded, anywhere. They are, almost certainly, the only two there will ever be.

Sources: Naval History and Heritage Command; Smithsonian National Air and Space Museum; NOAA Office of National Marine Sanctuaries (USS Macon wreck documentation); Smithsonian Magazine.