Article: Battle of Midway
Section: Initial air attacks

Question: When were two Japense carriers sighted, indicating an air strike en route?

Initial air attacks.
At about 09:00 on 3 June, Ensign Jack Reid, piloting a PBY from US Navy patrol squadron VP-44, spotted the Japanese Occupation Force some to the west-southwest of Midway.
He mistakenly reported this group as the Main Force.
Nine B-17s took off from Midway at 12:30 for the first air attack.
Three hours later, they found the Japanese Tanaka's transport group to the west.
Under heavy anti-aircraft fire, they dropped their bombs.
Though hits were reported, none of the bombs actually hit and no significant damage was inflicted.
Early the following morning Japanese oil tanker "Akebono Maru" sustained the first hit when a torpedo from an attacking PBY struck her around 01:00.
This was the only successful air-launched torpedo attack by the U.S. during the entire battle.
At 04:30 on 4 June, Nagumo launched his initial attack on Midway itself, consisting of 36 Aichi D3A dive bombers and 36 Nakajima B5N torpedo bombers, escorted by 36 Mitsubishi A6M Zero fighters.
At the same time he launched a defensive combat air patrol (CAP) with his eight search aircraft (one from the heavy cruiser launched 30 minutes late due to technical difficulties).
Japanese reconnaissance arrangements were flimsy, with too few aircraft to adequately cover the assigned search areas, laboring under poor weather conditions to the northeast and east of the task force.
Yamamoto's faulty dispositions had now become a serious liability.
As Nagumo's bombers and fighters were taking off, 11 PBYs were leaving Midway to run their search patterns.
At 05:30, PBY reported sighting two Japanese carriers with empty decks, indicating an air strike en route.
American radar picked up the enemy at a distance of several miles, and interceptors were scrambled.
Unescorted bombers headed off to attack the Japanese carrier fleet, their fighter escorts remaining behind to defend Midway.
At 06:20 Japanese carrier aircraft bombed and heavily damaged the U.S. base.
Midway-based Marine fighters, which included 7 F4Fs and 21 F2As, intercepted the Japanese and suffered heavy losses, though they managed to destroy four B5Ns and at least three A6Ms.
Within the first few minutes, 3 F4Fs and 13 F2As were destroyed, while most of the surviving U.S. planes were damaged, with only two remained airworthy.
American anti-aircraft fire was accurate and intense, destroying four additional Japanese aircraft and damaging many more.
Of the 108 Japanese aircraft involved in this attack, 11 were destroyed, 14 were heavily damaged, and 29 were damaged to some degree.
The initial Japanese attack did not succeed in neutralizing Midway: American bombers could still use the airbase to refuel and attack the Japanese invasion force, and most of Midway's land-based defenses were intact.
Japanese pilots reported to Nagumo that another aerial attack to soften Midway's defences would be necessary if troops were to go ashore by 7 June.
Having taken off prior to the Japanese attack, American bombers based on Midway made several attacks on the Japanese carrier fleet.
These included six Grumman Avengers, detached to Midway from the s VT-8 (Midway was the first combat mission for the VT-8 airmen, and it was the combat debut of the TBF), Marine Scout-Bombing Squadron 241 (VMSB-241), consisting of eleven SB2U-3s and sixteen SBDs, plus four USAAF B-26s, armed with torpedoes, and fifteen B-17s.
The Japanese repelled these attacks for the loss of two fighters, destroying five TBFs, two SB2Us, eight SBDs and two B-26s.
The first Marine aviator to perish in the battle, Major Lofton R. Henderson of VMSB-241, was killed while leading his inexperienced Dauntless squadron into action.
The main airfield at Guadalcanal was named Henderson Field after him in August 1942; two civil airports also bear this name.
One B-26, after being seriously damaged by anti-aircraft fire, veered into a steep dive straight toward the "Akagi".
Making no attempt to pull out of its run, the aircraft narrowly missed crashing directly into the carrier's bridge, which could potentially have killed Nagumo and his command staff.
This experience may well have contributed to Nagumo's determination to launch another attack on Midway, in direct violation of Yamamoto's order to keep the reserve strike force armed for anti-ship operations.