|Battle of the Coral Sea|
|Carrier battle, first day|
|Carrier battle, second day|
|Recovery, reassessment and retreat|
At 17:00 on May 3, Fletcher received information that US Army and RAAF reconnaissance aircraft based in Australia and New Guinea had sighted the Japanese Tulagi invasion force the day before approaching the southern Solomons. TF17 changed course towards Guadalcanal in order to be in position to launch airstrikes against the Japanese forces at Tulagi the next morning.
Air searches and decisions
At 08:16 on May 5, TF17 rendevouzed with TF11 and TF44 320 miles south of Guadalcanal. At about the same time, four fighter aircraft from Yorktown intercepted a Kawanishi Type 97 reconnaissance aircraft from the Yokohama (25th) Air Group based at Rabaul and shot it down about 11 miles from TF11. The aircraft was unable to send a report before it crashed, but when it failed to return to base the Japanese correctly assumed that it had been shot down by carrier aircraft.
A message from Pearl Harbor notified Fletcher that radio intelligence had deduced that the Japanese planned to land their troops at Port Moresby on May 10 and that the Japanese fleet carriers would likely be operating close to the invasion convoy. Armed with this information, Fletcher directed TF17 to refuel. After the refueling was completed on May 6, Fletcher planned to take his forces north towards the Louisiades and do battle on May 7.
On May 6, Fletcher absorbed TF11 and TF44 into TF17. Fitch was placed in tactical command of the carrier task groups. Believing that the Japanese carriers were still well to the north near Bougainville, Fletcher continued to refuel his ships. Reconnaissance patrols from the American carriers conducted throughout the day failed to locate any of the Japanese naval forces, because they were located just beyond the range of the US aircraft.
At 10:00, a Kawanishi reconnaissance aircraft from Tulagi sighted TF17 and notified its headquarters. Takagi received the report at 10:50. At that time Takagi's force was about 300 miles north of Fletcher, near the maximum range for carrier aircraft. Takagi, whose ships were still refueling, was not yet ready to engage in battle. He also concluded, based on the sighting report, that TF17 was heading south, away from him, and thereby increasing the range. Furthermore, Fletcher's ships were under a large, low-hanging overcast which Takagai and Hara felt would make it difficult for their aircraft to find the American carriers. Takagi detached his two carriers with two destroyers under Hara's command to head towards TF17 at 20 knots in order to be in position to attack at first light the next day while the rest of his ships completed refueling.
Land-based B-17s attacked the approaching Port Moresby invasion forces, including Gōto's warships, several times during the day on May 6 without success. MacArthur's headquarters radioed Fletcher with reports of the attacks and the locations of the Japanese invasion forces.
At 18:00, TF17 completed fueling and Fletcher detached Neosho with a destroyer, Sims, to take station further south at a prearranged rendezvous point. TF17 then turned to head northwest towards Rossel Island in the Louisiades. Unbeknownst to the two adversaries, their carriers were only 70 miles away from each other by 20:00 that night. At 20:00 Hara reversed course to meet Takagi who had completed refueling and was now heading in Hara's direction.
Late on May 6 or early on May 7, Kamikawa Maru set-up a seaplane base at Deboyne Island in the Louisiades in order to help provide air support for the invasion forces as they approached Port Moresby. The rest of Marumo's Cover Force then took station near the D'Entrecasteaux Islands to help screen Abe's oncoming convoy.