By June "Hornet"s air group (Carrier Air Group 2 (CVG-2)) mustered 40 Hellcat fighters, including 4 night-fighter versions, 33 Curtiss SB2C Helldiver dive bombers and 20 Avengers. Task Group 58.1 had exchanged "Cowpens" for "Hornet"s sister so it mustered a pair each of fleet and light carriers for the campaign. Task Force 58 departed Majuro on 6 June in time to begin the air strikes on the southern Marianas six days later, three days prior to the planned amphibious assault on Saipan, although the Japanese discovered that it had left Majuro on 8 June. "Hornet"s night fighters began shooting down Japanese reconnaissance aircraft on the night of 10 June. Vice Admiral Marc Mitscher, commander of the task force, decided to move the air strikes forward to 11 June, hoping to catch the Japanese off guard. The task group's fighters discovered 30 Zeros over Guam during their sweep and claimed to have shot them all down, with "Hornet"s 16 Hellcats claiming 23 of them as kills. A picket line of destroyers was stationed between the carriers and Guam and they controlled interceptions by the task group's fighters of about a dozen reconnaissance and attack aircraft that afternoon. The following days the task group continued to attack Guam to eliminate all of the aircraft based there as well as any reinforcements. Later that afternoon, "Hornet"s aircraft discovered a seven-ship reinforcement convoy east of Guam, but it was too far away to attack if the aircraft were to land during daylight. That night the task group closed the distance while the convoy continued to approach Guam and was only when it launched 20 bomb-armed Hellcats. Their pilots were not trained for anti-shipping missions and failed to significantly damage the ships of the convoy before it reached Guam.