What aircraft sank the gunboat USS Panay in 1937?

Since November, the Panay had been evacuating American citizens from the combat zone around Nanking. That task kept it sailing right at the front, on the same waters used by the retreating Chinese forces. Japanese air units stationed near Nanking had received information that those retreating forces were in the area aboard ten large steamers, and it was that report that sent Japanese aircraft against the ships on the river.

Asking for "the aircraft" that sank the Panay has no single answer, because the attack came in two waves with two different types of aircraft. First came three Yokosuka B4Y Type-96 bombers, which dropped eighteen 132 lb (60 kg) bombs from high altitude; of all of them, only two struck the gunboat. Then came the low-level work: nine Nakajima A4N Type-95 fighters strafed the ship. Between the bombing from above and the strafing from close in, the episode ended with the American gunboat and three tankers sunk.

The Aichi D1A, the Japanese carrier-based dive bomber of that era, is also credited with a presence in the action: several aircraft of this type took part in the Panay incident. Its design was not of domestic origin: Aichi obtained a German Heinkel He 66 and adapted it to meet the requirement it had to fulfill, a common route in the Japanese aircraft industry of the interwar period to reach an operational aircraft sooner.