A mixture of air and aviation gasoline in her improperly drained aircraft fueling trunk lines (which ran from the keel tanks to her hangar deck) ignited, causing a series of explosions and fires that could not be controlled.

[2] She was originally authorized in 1916 as a Lexington-class battlecruiser, but construction was delayed so that higher-priority anti-submarine vessels and merchant ships, needed to ensure the safe passage of personnel and materiel to Europe during Germany's U-boat campaign, could be built.

[18] The Navy's Bureau of Construction and Repair was not convinced when the class was being designed that aircraft could effectively substitute as armament for a warship, especially at night or in bad weather that would prevent air operations.

[25] In addition twenty-two 20-millimeter (0.8 in) Oerlikon AA guns were installed, six in a new platform at the base of the funnel, 12 in the positions formerly occupied by the ship's boats in the sides of the hull, two at the stern, and a pair on the aft control top.

[29] After fitting-out and shakedown cruises, Lexington was transferred to the West Coast of the United States and arrived at San Pedro, California, part of Los Angeles, on 7 April 1928.

[30] Lexington was based in San Pedro until 1940 and mainly stayed on the West Coast, although she did participate in several Fleet Problems (training exercises) in the Atlantic Ocean and the Caribbean Sea.

During Fleet Problem IX in January 1929, Lexington and the Scouting Force failed to defend the Panama Canal against an aerial attack launched by her sister ship Saratoga.

[31] Future science fiction author Robert A. Heinlein reported aboard on 6 July as a newly minted ensign under Captain Frank Berrien.

[32] Heinlein experienced his first literary rejection when his short story about a case of espionage discovered at the Naval Academy failed to win a shipboard writing contest.

The U.S. Navy sent Lexington, which had been at Puget Sound Naval Shipyard in Bremerton, to Tacoma, and heavy electric lines were rigged into the city's power system.

Fleet Problem XI was held the following month and Saratoga returned the favor, knocking out Lexington's flight deck for 24 hours, just as the exercise came to a climax with a major surface engagement.

Rear Admiral Joseph M. Reeves baited a trap for King with a destroyer and scored a kill on Lexington on 22 March while the latter's aircraft were still searching for Saratoga.

During the actual fleet problem, Lexington attempted to attack San Francisco, but was surprised in heavy fog by several defending battleships at close range and sunk.

Most notably during Fleet Problem XVI, April–June 1935, Lexington ran low on fuel after five days of high-speed steaming, and this led to experiments with underway replenishment that later proved essential to combat operations during the Pacific War.

[39] Admiral Claude C. Bloch limited Lexington to support of the battleships during Fleet Problem XVIII in 1937 and consequently the carrier was crippled and nearly sunk by surface gunfire and torpedoes.

Fleet Problem XX, held in the Caribbean in March–April 1939, was the only time before October 1943 that the Navy concentrated four carriers (Lexington, Ranger, Yorktown, and Enterprise) together for maneuvers.

[42] Admiral Husband Kimmel, Commander-in-Chief, Pacific Fleet, ordered Task Force (TF) 12—Lexington, three heavy cruisers and five destroyers—to depart Pearl Harbor on 5 December 1941 to ferry 18 U.S. Marine Corps Vought SB2U Vindicator dive bombers of VMSB-231 to reinforce the base at Midway Island.

On the morning of 7 December, the task force was about 500 nautical miles (930 km; 580 mi) southeast of Midway when it received news of the Japanese attack on Pearl Harbor.

Brown was ordered back to sea on 31 January to escort the fast oiler Neosho to its rendezvous with Halsey's task force returning from its attack on Japanese bases in the Marshall Islands.

Brown was reinforced by the heavy cruiser Pensacola and two destroyers on 17 February and tasked these ships to bombard Rabaul in addition to the attack by Lexington's aircraft.

While still some 453 nautical miles (839 km; 521 mi) northeast of Rabaul, the task force was spotted by a Kawanishi H6K "Mavis" flying boat on the morning of 20 February.

One Japanese Aichi E13A "Jake" floatplane succeeded in tracking the task force for a short time after dark, but six H6Ks launched after midnight were unable to locate the American ships.

[53] Nimitz promptly responded by ordering Yorktown's Task Force 17, under the command of Rear Admiral Frank Jack Fletcher, to rendezvous with Brown north of New Caledonia on 6 March to allow the latter to attack Rabaul.

Rear Admiral Aubrey Fitch assumed command of Task Force 11 on 1 April and it was reorganized to consist of Lexington and the heavy cruisers Minneapolis and New Orleans as well as seven destroyers.

Late on 18 April, the training was canceled, as Allied codebreakers had figured out that the Japanese intended to invade and occupy Port Moresby and Tulagi in the southeastern Solomon Islands (Operation Mo).

Therefore, Fitch's ships, acting on a command from Nimitz, rendezvoused with TF 17 north of New Caledonia on 1 May, after refueling from the tanker Kaskaskia on 25 April to thwart the Japanese offensive.

US Army Air Forces (USAAF) aircraft spotted Shōhō[Note 1] southwest of Bougainville Island on 5 May, but she was too far north to be attacked by the American carriers, which were refueling.

Based on this information, Fletcher planned to complete refueling on 6 May and to move closer to the eastern tip of New Guinea to be in a position to locate and attack Japanese forces on 7 May.

[63] American reconnaissance aircraft reported two Japanese heavy cruisers northeast of Misima Island in the Louisiade Archipelago off the eastern tip of New Guinea at 07:35 and two carriers at 08:15.

A number of them flew right beside the American ships, flashing signal lights in an effort to confirm their identity, but they were not initially recognized as Japanese because the remaining Wildcats were attempting to land aboard the carriers.