This meant that the torpedoes could not be struck below until after all the bombs were moved up from their magazine, assembled and mounted on the aircraft. This process normally took about an hour and a half; more time would be required to bring the aircraft up to the flight deck, and to warm up and launch the strike group. Around 07:40, he reversed his order when he received a message from one of his scout aircraft that American warships had been spotted. Depleted of ammunition, two of "Hiryū"s CAP Zeros landed aboard the carrier at 07:40. At 07:55, the next American strike from Midway arrived in the form of 16 Marine Douglas SBD Dauntless dive bombers of Marine Scout Bomber Squadron (VMSB-241) under Major Lofton R. Henderson. "Hiryū"s 3 CAP fighters were among the 9 still aloft that attacked Henderson's planes, shooting down 6 of them as they executed a fruitless glide bombing attack on "Hiryū". In return, the gunner of one of the Dauntlesses shot down one of "Hiryū"s Zeros. At roughly the same time, the Japanese carriers were attacked by 12 USAAC B-17s, bombing from . The high altitude of the B-17s gave the Japanese captains enough time to anticipate where the bombs would land, and they successfully maneuvered out of the impact area. Four B-17s attacked "Hiryū", but missed with all their bombs. "Hiryū" reinforced the CAP with launches of 3 more Zeros at 08:25. These fresh Zeros helped defeat the next American air strike from Midway, 11 Vought SB2U Vindicator dive bombers from VMSB-241, which attacked the battleship "Haruna" starting around 08:30. "Haruna" escaped damage and 3 of the Vindicators were shot down. Although all the American air strikes had thus far caused negligible damage, they kept the Japanese carrier forces off-balance as Nagumo endeavored to prepare a response to news, received at 08:20, of the sighting of American carrier forces to his northeast. "Hiryū" began recovering her Midway strike force at around 09:00 and finished shortly by 09:10. The landed aircraft were quickly struck below, while the carriers' crews began preparations to spot aircraft for the strike against the American carrier forces. The preparations were interrupted at 09:18, when the first attacking American carrier aircraft were sighted.