The current model flight suit for the US military is the CWU 27/P and is available in sage green and desert tan. Commercial flight suits for civilian flying are also available, and are frequently used by helicopter crew (including non-pilots such as flight engineers, paramedics, and nurses), aerobatic pilots, and others who desire a practical "uniform". Although there are multiple pockets on the current CWU 27/P flight suit, all pockets are placed on the front of the flight suit or on the arms or legs. There are no pockets on the back of the flight suit. This design allows easier access to the pockets while the wearer is sitting (such as in the cockpit of an aircraft), and ensures that the wearer in a seated position does not have to sit on any items in a back pocket (such as a wallet). Members of the United States Marine Corps wore flight suits during most vehicle patrols and ground combat operations in Iraq and Afghanistan, because their standard camouflage utilities were not flame-resistant. Flight suits have now been phased out among ground personnel with the introduction of the Flame Resistant Organizational Gear, or "FROG" suit, which resembles the standard camouflage utilities. NASA astronauts have worn one-piece flight suits when in training or on flights in their NASA T-38s. The current flight suit worn by astronauts is royal blue, made of Nomex. The now-common "shirt-sleeve environment" of the orbiting Space Shuttle and International Space Station has resulted in much more casual attire during spaceflight, such as shorts and polo shirts. In the pre-"Challenger Disaster" era, Shuttle crews wore light blue flight suits and an altitude helmet during launch/reentry. Apollo crews wore white 2-piece beta cloth uniforms during non-essential activities and the full A7L pressure suit during launch, trans-lunar injection, lunar ascent/descent, and EVAs. Mercury and Gemini crews wore their space suits for the duration of the mission, with the exception of Gemini 7. Pilots and flight crews use several colors of flight suit. NASA crews, for example, wear blue flight suits as a sort of functional dress uniform during training. The orange suits that they wear during launch and re-entry/landing are designed for high visibility, should there be an emergency recovery. White suits are worn during space walks to control temperature. NASA non-astronaut flight crew at Langley Research Center wear blue, and crew at the Dryden Flight Research Center wear either green or desert tan, and all newer suits issued are desert tan.