In 1923 Tennessee, two best friends, Rafe McCawley and Danny Walker, play together in the back of an old biplane, pretending to be soldiers fighting the German Empire in World War I. When Danny's drunk father comes and attacks Danny, Rafe defends him and calls Danny's father a "dirty German", in which he reveals that he fought the Germans in France during World War I and prays the boys never encounter the horrors he saw.
In January 1941, with World War II raging, Danny and Rafe are both First Lieutenants under the command of Major Jimmy Doolittle. Doolittle informs Rafe that he has been accepted into the Eagle Squadron, a RAF outfit for American pilots during the Battle of Britain. Rafe meets a nurse named Evelyn, who passes his medical exam despite his dyslexia. That night, Rafe and Evelyn enjoy an evening of dancing at a nightclub and later, a jaunt in the New York harbor in a borrowed police boat. Rafe shocks Evelyn by saying that he has joined the Eagle Squadron and is leaving the next day. During a mission to intercept a Luftwaffe bombing raid, Rafe is shot down over the English Channel and is presumed killed in action. A mourning Evelyn finds comfort in Danny, leading to a romance between the two, and they take a romantic night in an army plane up in the clouds, and a romantic swim at the beach. Meanwhile, the Imperial Japanese Navy begins to plot a surprise attack on the Pacific Fleet at Pearl Harbor after the US had cut off their oil supply. They send in spies to survey the naval ships and airfields, modify aerial torpedoes for the shallow harbor, and send a series of confusing messages that expressing a hope for peace.
On the night of December 6, Evelyn is shocked to discover Rafe standing outside her door, having survived his downing and been picked up by a French fishing boat and spending the ensuing months trapped in Nazi-occupied France. Rafe, in turn, discovers Danny's romance with Evelyn and leaves for the Hula bar feeling betrayed, where he is welcomed back by his overjoyed fellow pilots. Danny finds a drunken Rafe in the bar with the intention of making things right, but the two get into a fight. They drive away, avoiding being put in the brig when the military police arrive at the Hula bar.
The next morning, on December 7, the Imperial Japanese Navy begins its attack on Pearl Harbor. The US Pacific Fleet suffers severe damage in the surprise attack, and most of the defending airfields are obliterated before they are able to launch fighters to defend the harbor. Rafe and Danny manage to take off in P-40 fighter planes, and are able to shoot down several of the attacking planes. They later assist in the rescue of the crew of the capsized USS Oklahoma, but are too late to save the crew of the sinking USS Arizona. Meanwhile, Evelyn and the other medical staff are overwhelmed with the amount of wounded and dying patients and one of her fellow nurses, Betty, is listed among the casualties.
The next day, President Franklin Delano Roosevelt delivers his Day of Infamy Speech to the nation and requests the US Congress declare a state of war with the Empire of Japan. Later, Danny and Rafe are both assigned to travel stateside under newly promoted Lt. Colonel Doolittle for a secret mission. Before they leave, Evelyn reveals to Rafe that she is pregnant with Danny's child, and intends to stay with Danny even though she will always love him deep down.
