The short answer: the Japanese got more of their planes to the enemy carriers. About 8 times as many Japanese bombers attacked the US carriers as US bombers attacked the Japanese carriers. This mismatch in numbers was also responsible for the very heavy Japanese aircraft and aircrew losses, due to effective US anti-aircraft gunnery.

First, the Japanese had more combat aircraft at the battle:

• Japan: 87 A6M Zeros, 68 Aichi D3A (Val) dive bombers, 57 Nakajima B5N (Kate) torpedo bombers

• USA: 63 Grumman F4F Wildcats, 47 Douglas SBD Dauntless dive bombers, 26 Grumman TBF Avengers torpedo bombers

The Japanese had about 70% more carrier-based bombers, and all else being the same, could be expected to hit the enemy carriers about 70% more times.

Second, the Japanese aircraft had better luck finding their targets. The Japanese launched three strikes each from their two carrier forces:

• First strike (Zuikaku and Shokaku): 64 aircraft, with 21 Vals and 20 Kates. This strike attacked Hornet, with 15 Vals and 20 Kates attacking (the others Vals had been shot down or forced to abort due to US CAP (i.e., fighter cover)). Hornet was hit by 3 bombs, 2 torpedoes, and 2 crashing aircraft.

• Second strike (Zuikaku and Shokaku): 44 aircraft, with 19 Vals and 16 Kates. Attacked Enterprise and her companions, with 17 Vals and 12 Kates attacking, for 2 bomb hits on Enterprise.

• Third strike (Junyo): 29 aircraft, with 17 Vals. Attacked Enterprise and her companions, with 17 Vals, missing Enterprise and damaging South Dakota and San Juan.

• Fourth strike (Junyo): 15 aircraft, with 7 Kates. Attacked Hornet, which was being towed at low speed, with 7 Kates, for 1 torpedo hit on Hornet, which doomed her.

• Fifth strike (Zuikaku; Shokaku was now out-of-action due to heavy damage): 14 aircraft, with 2 Vals and 7 Kates (armed with bombs). Attacked Hornet, for 1 bomb hit.

• Sixth strike (Junyo), 10 planes, with 6 Vals. Attacked Hornet, for 1 bomb hit.

Meanwhile, the US strikes were:

• First strike (Hornet): 29 aircraft, with 15 Dauntlesses and 6 Avengers. 11 Dauntlesses attacked Shokaku, for at least 3 bomb hits, which put Shokaku out of action. The Avengers didn't find the Japanese carriers, and attacked the cruiser Tone, missing with all torpedoes. Tone was part of the Japanese "Vanguard Group" of battleships and cruisers.

• Second strike (Enterprise): 20 aircraft, with 3 Dauntlesses and 9 Avengers. Attacked the Vanguard Group, and hit the cruiser Chikuma with 1 bomb.

• Third strike (Hornet): 26 aircraft, with 9 Dauntlesses and 10 Avengers. Attacked the Vanguard Group, and hit the cruiser Chikuma with 2 bombs and 1 torpedo.

The Vanguard group absorbed so many attacks because they were closer to the US carriers. The first US strike spotted them, and continued on to find and attack the Japanese carriers (at least, the Dauntlesses found and attacked them).

The US forces did have luck - before the airstrikes were launched, two Dauntlesses (on patrol, searching for the Japanese ships) found and attacked the light carrier Zuiho, hitting with 2 bombs, putting her out of action.

In summary, the Japanese attacked Hornet and Enterprise with 103 bombers, with a total of 10 hits on the two carriers. The US attacked Shokaku with 11 bombers, for 3 to 6 hits, and Zuiho with 2 bombers, for 2 hits.

Clearly, the US bombing was far more accurate. This was due in at least part due to the very effective US anti-aircraft gunnery, which shot down over half of the Japanese bombers that attacked. This anti-aircraft fire was the main cause of the very heavy Japanese aircraft and aircrew losses (99 aircraft and 148 aircrew). The Japanese CAP and escorting fighters were effective, and were the main cause of the loss of 26 US aircrew. The US lost many aircraft, 81 in total, but many of these losses were due to aircraft ditching when they were unable to land on returning to the US carriers - most of the ditching aircrew were rescued.