[1] This led to the idea of the United States obtaining a pair of German airships as part of the reparations plan, but they were destroyed by their crews in 1919.

The first ship of the class, R38, was already under construction, and so an agreement was reached in October 1919 to sell the incomplete airship to the United States, which gave it the designation ZR-2.

During a test flight in August, ZR-2 experienced a catastrophic structural failure and crashed into the Humber Estuary, killing all but five aboard.

The loss of Shenandoah in a crash in Ohio in September 1925 did not interrupt this; indeed, the incident left the US Navy with only one rigid airship that, under the terms of her construction, was not permitted to take part in military operations.

As part of this collaboration, Luftschiffbau Zeppelin's Chief Stress Engineer, Karl Arnstein, went to the United States to work with Goodyear on new designs and techniques.

[9] Similarly, rather than using a single structural keel along the underside of the hull, Arnstein's design had three, triangular shaped keels - one along the top of the airship, which was used to provide access to the valves of the ship's gas cells, and two more placed at 45 degree angles on each side of the bottom of the hull, which supported the engine compartments and crew spaces.

This design change came about following an incident involving the German passenger airship Graf Zeppelin, which, when taking off in 1929, had almost struck a set of power lines with its lower fin, which could not be seen from the ship's control gondola.

[11] When the decision was taken to use helium instead of hydrogen in 1922, Shenandoah was fitted with a set of condensers to allow the collection of water vapor from the engine exhausts to create ballast and manage the ship's buoyancy.

The Akron class required three times more gas to fill the cells, which made the collection of water more important, in spite of the increased availability of helium through improvements in production, transport and storage.

One significant innovation of the Akron class airships was the inclusion in the hull of a 75-by-60-by-16-foot (22.9 m × 18.3 m × 4.9 m) hangar capable of accommodating up to five small airplanes for use as scouts and fighters.

In the USS Akron, however, structural girders obstructed the two rearmost hangars, meaning it was capable of accommodating no more than three aircraft when first commissioned.

Initially, the Navy envisaged the air group providing fighter protection for the airship, with the ship undertaking the scouting and thus proceeding right over the enemy.

[9] For this reason, the primary aircraft carried was the Curtiss F9C Sparrowhawk, a small biplane fighter armed with a pair of .30 in M1919 machine guns that was more suited to the air defense mission rather than reconnaissance.

The Navy, over the objections of many officers such as Charles E. Rosendahl, who had commanded both Los Angeles and Akron, elected to alter the mission of the airship from direct scout to genuine airborne aircraft carrier, leaving the reconnaissance to the air group.

To extend the Sparrowhawk's range, the planes were modified to accommodate an additional external fuel tank, capable of carrying up to 30 US gallons (110 L).

[19] The installation of the fuel tank, along with RDF equipment, led to suggestions that the aircraft could scout an area up to 200 miles in any direction from the ship.

The ship was christened on 8 August 1931 by the First Lady, Lou Henry Hoover, undertook her first flight trial on 23 September, and was commissioned on 27 October.

The ship was caught in a storm off the coast of New Jersey and crashed just after midnight on 4 April, killing 73 people on board, including Rear Admiral William Moffett, the Chief of the Bureau of Aeronautics.

Between November 1933 and January 1934, Macon undertook a number of exercises with the fleet, being "shot down" on many occasions by both carrier-based aircraft and anti-aircraft fire.

In early 1935, the ship participated in further exercises until, on 12 February, while returning to Moffett Field, having lost one of her stabilizers, it made a forced landing in the sea off Point Sur, sinking with the loss of two of her crew.

[18] The ZRCV concept, which planned for a 9.55 million cu ft (270,000 m3) rigid airship — significantly larger than the Akron class — capable of carrying up to nine Douglas-Northrop BT-1 dive bombers.

However, the loss of Macon in February 1935, combined with President Roosevelt ordering a limitation on the size of new airships, meant ZRCV was never more than an idea.