First seen in The Avengers #61, the Quinjet was designed by T'Challa with help from the Wakanda Design Group. The original could transport up to seven members of the team anywhere in the world and had a top speed of mach 2.1. The design is constantly being upgraded to make sure it remains cutting edge technology.
They boast VTOL technology and are adaptable to space, deep-sea and even standard flight modes. They are stored in the third floor of the Avengers mansion.
Used primarily by the Avengers.
In Avengers: Disassembled, Scarlet Witch's reality altering powers caused it to explode. However, when the Avengers Reassembled six months later, Tony Stark ( Iron Man) had a new Quinjet brought in (or perhaps it was another of the old Quinjets). After Civil War, several Quinjets were made, which turned out to be a good thing, since Ares crashed it during a fight with Doombots. When he did so, it was revealed that a Quinjet cost over 250 million dollars.
The Quinjets were used by Norman Osborn and are the Dark Avengers during the "Dark Reign" but have since been returned to Tony Stark and Avengers proper following the siege of Asgard.
In Other Media
The Avengers: Earths Mightiest Heroes (2010)
Various Quinjets are used in the series, developed by Stark Industries. The Quinjets are shown to be capable of space travel in several episodes.
Iron Man: Armored Adventures (2009)
Black Panther pilots a Quinjet in the series finale. Like in the comics, the Quinjet is shown to be built by Wakandan scientists rather than SHIELD.
Quinjets are heavily featured in the live-action film, as property of SHIELD. In the climax, Captain America, Hawkeye, and Black Widow hijack one in order to get to New York City and fight off the Chitauri invasion. This Quinjet ends up being destroyed by Loki, but the heroes survive the crash.