The ambush of Gray Flight was a battle of the Galactic Civil War.
Believing the interruption of a Rebel mission to Dominus III scouting for a new base by Imperial forces to be the result of a spy within the Rebel Alliance, Mon Mothma established a covert unit led by Princess Leia Organa, flying prototype T-65 X-wing starfighters and tasked with both identifying the source of the intelligence leak and locating a new home for the Alliance. To that end, Organa, as Gray Leader, divided the pilots of Gray Flight into three groups to scout potential base sites, taking Gray Two Wedge Antilles and Gray Three Tess Alder to the Pybus system.
At the same time, command of Darth Vader's Imperial Star Destroyer Devastator was transferred to Colonel Kell Bircher. Bircher—in reality a Rebel spy and nephew of Mon Mothma—was given a mandate by Emperor Palpatine to hunt the Rebel Alliance, and tracked Gray Flight to Pybus.
Arriving in system, Organa, Antilles, and Alder briefly observed the planet below before the arrival of Bircher's Star Destroyer and an Interdictor cruiser, which activated its gravity well projectors, preventing the Rebel pilots from fleeing. To avoid the capital ships' turbolaser fire, Organa ordered Alder to orbit in the shadow of Pybus' moon while she and Antilles dove towards the planet's atmosphere. The Imperial forces responded with an orbital bombardment, driving the Rebels to regroup and go on the offensive. Against Organa's order to go to ground, Alder joined the other two pilots in launching a torpedo volley against the two squadrons of TIE/IN interceptor deployed by Devastator, destroying eleven of the enemy craft. Colonel Bircher, commanding his men from the cockpit of a proton torpedo, hyperdrive, and deflector shield-equipped interceptor, ordered the remaining TIEs to pursue the three X-wings as they approached the Star Destroyers, preventing the capital ships from firing on the Rebels for fear of striking their own forces. As the TIE pilots realized the ploy and broke off their attack, Organa had her subordinates lock on to her starfighter's transponder, which she jettisoned near the Interdictor, guiding the torpedoes into its gravity well projectors and allowing the flight to escape into hyperspace. However, Bircher had prepared a contingency, launching a TIE/sa bomber in pursuit. The bomber detonated upon reversion, injuring Organa and crippling her starfighter.
Receiving a warning from the spirit of Jedi Obi-Wan Kenobi that Organa was in danger, grounded Gray Flight pilots Luke Skywalker and Prithi had R2-D2, Skywalker's astromech droid, retrieve her coordinates, defying the Princess' orders in a rescue attempt.
Refusing to abandon the flight leader, despite her orders and the threat of the Imperial force's impending arrival, Antilles had Organa use her still-functioning maneuvering thrusters to move away from their reversion coordinates, distancing herself from an Imperial attack, while her astromech droid, R2-T4, pressurized her flight suit to slow her bleeding, and Alder reported the arrival of Skywalker and Prithi. At the Princess' direction, Luke removed a pair of fuel cells from her X-wing, binding them to a proton torpedo and his chronometer, set to broadcast a distress signal, and pushed the bundle off into space. Upon the Imperial group's arrival, the X-wing pilots launched another torpedo volley, passing the oncoming interceptors, and striking Skywalker's improvised explosive device. Realizing too late that his squadrons were not the intended target, Bircher jumped to hyperspace to escape the blast, and ordered Devastator to follow. The Alliance pilots did the same, slaving the now-unconscious Organa's navigation computer to their own as they jumped to coordinates provided instinctively by Skywalker through the Force.
Upon her return to the Alliance Fleet, Leia Organa was given treatment by a 2-1B surgical droid and placed into a bacta tank to recuperate, her life saved by R2-T4's efforts.