The STS-121 Space Shuttle crew, including ESA astronaut Thomas Reiter, arrive at NASA's Kennedy Space Center, in Florida, the United States, ahead of the Terminal Countdown Demonstration Test (TCDT). The STS-121 crew arrived in a NASA Gulfstream G-2 aircraft. The TCDT is held before each Space Shuttle flight and provides the crew with an opportunity to participate in safety training and simulated countdown activities.