On August 3, 1953, test pilot E.D. "Sam" Shannon pushed a strange, delta-winged aircraft across San Diego Bay on a pair of retractable hydro-skis, lifted off the water, and broke the sound barrier. The aircraft was the Convair XF2Y-1 Sea Dart, and it remains the only seaplane in history to fly faster than Mach 1. Three years later, the program was dead.

The Sea Dart was born of a real Navy problem. In 1948, jet fighters needed long, smooth runways — and aircraft carriers of the era struggled to operate the new generation of swept-wing jets at the speeds they required. Catapults were marginal. Arresting gear was being torn apart. The Navy issued a request for a water-based supersonic interceptor that could operate from any sheltered harbor or even be refueled by a submarine at sea.

Convair's answer was elegant. The fuselage was a watertight hull. Two Westinghouse J46 turbojets were mounted high on the back, intakes well above the spray. For takeoff, two hydro-skis extended hydraulically from the belly. At about 10 knots the hull lifted clear of the water; at 55 knots the aircraft was riding only on the ski tips; at 145 knots it left the water entirely. Landings reversed the sequence. The delta wing — designed by the same team that produced the F-102 — handled supersonic flight.

It worked. Five aircraft were built. The second prototype reached Mach 1.075 in a shallow dive. But the program ran into a wall of problems:

• The J46 engines underperformed — the planned afterburning version was never delivered, leaving the Sea Dart underpowered for level supersonic flight.
• Hydro-ski vibration at high speed was brutal. Pilots described it as being shaken inside a paint mixer.
• One fatal crash on November 4, 1954, killed Convair test pilot Charles E. Richbourg when the prototype broke apart over the bay during an airshow demonstration.
• Steam catapults, perfected by the British and adopted by the US in 1954, suddenly made conventional carrier jets practical at any speed. The Sea Dart's reason for existing evaporated.

The program was canceled in 1957. The surviving airframes sit in museums in San Diego, Pensacola, and the Bronx.

Why revisit it now? The strategic problem the Sea Dart solved has quietly returned. China's anti-ship ballistic missiles — the DF-21D and DF-26 — have made fixed runways and aircraft carriers vulnerable in ways unimaginable in the 1950s. A dispersible, water-based fighter that needs no runway, no catapult, and no fixed base is suddenly interesting again. And the engineering obstacles have largely dissolved:

• Modern composite hulls using carbon fiber and Kevlar can absorb impact loads that aluminum could not, eliminating the structural fatigue that doomed Richbourg.
• Active vibration damping and computer-controlled hydro-ski geometry could tame the shake that crippled the original.
• Modern turbofans like the F414 deliver more than double the thrust-to-weight of the J46, with vastly better fuel efficiency.
• Fly-by-wire makes the marginal stability of a high-mounted-engine seaplane trivial to manage.

China's AVIC AG600 amphibious aircraft, which flew in 2017, demonstrates that large-scale seaplane engineering is alive and well. The pieces exist. What's missing is the willingness to look at a 70-year-old solution to a problem we just rediscovered.