Doubts also linger regarding the command position onboard the final flight of space shuttle Endeavour, due to take place 19th April 2011. Current official man in charge of STS-134 Mark Kelly, remains at the hospital bedside of his wife US Congresswoman Gabrielle Giffords, who was seriously wounded in the shooting incident in Tucson, Arizona on 8th Jan 2011, in which six people were killed. Back-up commander Rick Sturckow has been put on standby.
Shuttle crew replacement has occasionally occurred over the years, though not usually at such a late stage. To try and prevent preflight injuries NASA has a list of high risk activities that astronauts assigned to flights are not allowed to take part in, such as skiing, parachuting, and motorcycle riding. Riding a bike, however, is not currently on the banned list!