Various pieces of wreckage of Oceanic Flight 815 ended up in numerous locations on and near the Island after the plane suffered a mid-air break-up and subsequently crashed on September 22, 2004. Those pieces and locations have been revealed, and occasionally revisited, in various episodes throughout the first four seasons of Lost.
The front section included the cockpit and, counting by the windows, the complete First Class with a maximum of 30 passengers. It crashed in a valley in the jungle, close to the beach where the middle section crashed.
Seth Norris, the plane's pilot, is the only known survivor from the front section. The co-pilot died in the impact, and the passengers in the front section appear to have suffered a similar fate. However, Jack did not check any of these passengers for signs of life.
The front section was discovered the day after the crash by Jack, Kate and Charlie, and originally tilted up at an angle. As they climbed up towards the cockpit, they passed several dead passengers still strapped into their seats. There were several empty seats, however, posing the question of whether or not passengers from that section of the plane survived. Shortly after pilot Seth Norris was found to be alive, he was pulled out of the cockpit by the Monster, and subsequently killed. Immediately following this, the tilted cockpit fell down flat onto the ground. Scared by the Monster, Jack, Kate and Charlie fled the cockpit and returned to their beach camp. ("Pilot, Part 1")
More than three months after the crash, the front section served as a rendezvous point for the survivors after they had successfully contacted the freighter. It was here that the survivors split into two groups: Jack's group, who believed that the people on the freighter were coming to rescue them, and Locke's group, who decided to heed Ben and Charlie's warnings that the people aboard the freighter weren't who they said they were. Shortly before Daniel Faraday jumped off the helicopter piloted by Frank Lapidus, the helicopter briefly hovered over the front section of the plane, shining a spotlight at it. ("The Beginning of the End")
The middle section crashed on a beach distant from the Barracks. It included part of the Business Class where Boone and Shannon had been seated. At least 48 passengers from the middle section survived the immediate crash, although Gary Troup died when he was sucked into an engine, causing it to explode. An unstable, tilted wing also exploded when it crashed to the ground, although presumably no-one died from this. ("Pilot, Part 1") ("Pilot, Part 2") ("Walkabout")
Part of the wreckage of the middle section was used by the middle section survivors to build various shelters along the beach. A few days after the crash, wild boars, attracted by the scent of the dead bodies inside, started to rummage through the wreckage. As a result, the survivors decided to burn the fuselage with the dead bodies inside. ("Walkabout")
About three weeks after the crash, a sudden change in the tide prompted the middle section survivors to move their camp further down the beach. Subsequently, the middle section fuselage wreckage has never been seen since outside flashbacks. ("Whatever the Case May Be")
Part of the plane's cargo compartment was found by Jack near the caves, along with various objects that were in it, including luggage, a coffin and dolls. ("White Rabbit") A day later, Jack led Kate, Charlie and Locke to the caves and told the latter two to look out for medical drugs. ("House of the Rising Sun")
The tail section crashed into the ocean on the western side of the island as compared to the middle section, closer to the Barracks. ("A Tale of Two Cities") Twenty-two people from the tail section initially survived the crash, nearly all of whom had to swim to the nearby beach. Some smaller pieces of wreckage also landed on the beach. These survivors are often known as the "Tailies".
Shortly after all the survivors had made it to the beach, the tail section sank. ("The Other 48 Days")
The day after the crash, a pair of seats from the middle section was put up on the beach, allowing Claire to rest on them. ("Pilot, Part 1") Sawyer also appropriated a seat for his own use, propped in front of his tent.
Another pair of Flight 815 seats was discovered underwater in a pond by Kate and Sawyer about three weeks after the crash. Still strapped to the seats were two dead passengers, one male and one female. Marshal Mars' Halliburton case, Nikki's Exposé script bag and various debris also ended up inside the pond with those seats. ("Whatever the Case May Be") ("Exposé")
Another pair of seats from the tail section of the plane ended up perched up in a tree. Bernard was found still strapped to one of the seats by Ana Lucia and Goodwin only minutes after the crash, while the passenger sitting next to him was already dead. Bernard was able to unbuckle his seatbelt and grab the tree before the seats fell out of the tree and crashed down to the ground, thus ensuring his survival. ("The Other 48 Days")
More than two months after the crash, purported wreckage of Flight 815 was discovered by remote operated vehicles deployed by a salvage ship, Christiane I, in the Sunda Trench near the Indonesian island of Bali. Footage of the bodies of crew members and passengers were released to the media for television broadcast, and an information hotline for their family members was established by the U.S. National Transportation Safety Board. However, Frank Lapidus, upon watching a news broadcast about the discovery of the wreckage, quickly came to the conclusion that a body claimed to be that of the plane's pilot, Seth Norris, wasn't actually him. ("Confirmed Dead")
An alternate version of the events leading up to the discovery of the wreckage was depicted in the Find 815 alternate reality game. Here, it was a single ROV operated by Sam Thomas, whereas in "Confirmed Dead", two ROVs were used, one of them being operated by a man named Ron and the other by an unnamed fellow crew member of his.