In June 1950, at an American Army base in Kimpo, South Korea, Capt. George Slocum, pilot of an L5 single-engine surveyor plane, receives orders delivered by his friend, Lt. Jerry Barker, to return to Japan briefly. Pleased at the opportunity to see his wife, George agrees to also meet Jerry's younger brother, Lt. Pete Barker, who is arriving from the States. Pete lands in Tazuke, Japan before George and, believing that Jerry is flying in to meet him, takes up one of the L5s to intercept him. George is confused by Pete's flying acrobatics and only on the ground does Pete realize his error. George gives Pete a mild reprimand but when the military police arrive to arrest the men for stunt flying over the city, both George and Pete insist they were practicing legitimate escape maneuvers. Later, while Pete attempts to romance Kate, an Army nurse, George surprises his wife Nancy, who is concerned over his sudden appearance. George suspects military action is imminent, but is unable to reassure Nancy. Soon after his arrival, however, George is recalled as the base receives news of North Korea's attack on South Korea. George and Pete are ordered to Pusan, Korea, but upon approach, are diverted to Seoul because of North Korean bombings. En route, the L5s pass over the smoking remains of Kimpo base and both planes land. Pete finds Jerry critically wounded and delirious. When Pete and George attempt to get Jerry to safety, they are attacked by armed civilian sympathizers. Jerry is killed and George and Pete fight off their attackers. George frees Korean teenager Clancy, the base mascot, and takes him on board. The planes take off and remain low for cover, but Pete drifts into a reverie while recalling Jerry and inadvertently gains altitude and the attention of an enemy fighter squad. George manages to divert the planes from Pete and, through dangerous flying, forces one to crash into the hills, dispersing the others. Despite successfully transporting the U.S. Ambassador and the Korean President to safety in Japan, Pete remains resentful over the uselessness of the unarmed surveyor planes, and wants revenge for Jerry's death. Pete has mechanic Swenson assist him in attaching a bazooka to one of his plane's wings. On the next mission, when Pete and George spot several enemy tanks, Pete disregards George's admonition and attempts to bomb one. Instead he is shot down. After flying over to verify that Pete is safe, George continues on his mission alone, to Pete's outrage. Upon returning to base, George asks Maj. Hacker to send men back to retrieve Pete, but Hacker refuses, explaining that their men have been cut off and are fighting for survival. Hacker orders George to drop desperately needed medical supplies at a nearby base and, taking a nervous Swenson with him, George complies. When George spots another tank brigade in a valley just beyond South Korean troops, he steers the Koreans over the river to make an unexpected rear assault. As George and Swenson return to base, Pete is escorted into camp by South Koreans, and George chastises Pete for wasting a plane through his recklessness. Pete grudgingly apologizes and over the next several weeks, he and George fly a series of missions dropping supplies and directing artillery fire and troops. While on guard one evening at another base, George spots a sneak enemy attack, but is seriously wounded in the assault. Pete volunteers to fly George out for proper medical attention and, despite George's feeble plea not to endanger the plane, daringly flies out. Airborne, Pete hears the transmission of American fighter pilots admitting they are disoriented due to heavy smoke and bemoans the lack of radio power that would allow him to guide them to their target. Upon landing at the medical base, Pete turns George over to Kate, before learning his home base has been over run. Later that night Kate tells Pete that George has died, but encourages him to see that his death was not in vain. When Swenson and his partner, Maxie Steiner, arrive with as much equipment as they could take from the base, Pete orders them to help him install a powerful radio in his L5. Although reprimanded for making an illegal flight getting George out, Pete receives orders for a mission to photograph key bridges for a possible retreat. Pete takes Maxie aloft with him and although Maxie laments their assignment, Pete orders him to comply. Just before returning, Pete spots a tank brigade through the battle smoke and radios the fighter jets to direct them to the tanks, which then are successfully destroyed. Pete is shot in the arm, forcing Maxie to fly the plane back to base. Pete and Maxie survive the crash landing, determined to put all their efforts toward fighting and winning the war.