In the early days of the war, Japan's primary scout plane was a three-seat reconnaissance biplane, the Kawanishi E7K flying boat. The plane, flown from land or launched by a ship, was codenamed "Alf" by the Allies. During the battle of the Coral Sea, Japanese cruisers used E7Ks to scout for Allied ships. Decommissioned in 1943, several E7Ks attempted kamikaze attacks against Allied ships in the latter days of the war.
The Kawanishi H6K flying boat, codenamed "Mavis" by Allied forces, was Japan's only four-engined, long-range reconnaissance float plane during the early part of the war. Though armed with four machine guns and a 20mm cannon, the large plane proved vulnerable to Allied fighters. A variation of the plane served as an air transport with the ability to ferry 18 troops. Allied planes discovered and destroyed Five H6Ks at Tulagi on May 4. American fighters also pursued and destroyed a lone Rabaul-based Mavis scouting the Coral Sea on the morning of May 5.
The Mitsubishi G4M "Betty" became the primary Japanese land-based bomber shortly after the raid on Pearl Harbor. The plane, designed for maximum range and speed, proved exceptionally vulnerable to Allied fighters. In addition to the plane's attack role, its great range made it valuable for scouting and transport purposes. Admiral Isoroku Yamamoto died on-board a G4M attacked by American P-38s. During the battle of the Coral Sea three Bettys from the Japanese base at Rabaul joined the search for the Allied fleet.
Strategic bombing was the primary role of the B-17 Flying Fortress. However, in the resource-strapped Pacific theater the bombers also provided reconnaissance and transport capabilities when required. During the Battle of the Coral Sea, B-17s of the 90th Bombardment Squadron sighted the Japanese invasion fleet. The information proved useful to Navy Admiral Frank J. Fletcher in thwarting the invasion. B-17s also participated in bombing attacks against the Japanese fleet.