ISS Flight 2A (Unity) was launched aboard the Space Shuttle Endeavour on STS-88.

Launch Date: December 4, 1998

The "2" indicates that the flight was the second in a planned series of flights to construct the International Space Station (ISS). The "A" indicates that it is an American launch to the ISS. The Flight 2A element (also known as Unity) actually consists of three hardware elements. They are the two Pressurized Mating Adapters (PMA's 1 and 2) mounted at either end of Unity and the Node that provides an intersection with 6 different docking ports for future ISS flight elements.