Robin Williams and his family-vacation romp RV cruised to the top of the US box office with a $16.4 million (GBP9.4 million) haul this weekend (29-30APR06), while September 11th (01) drama UNITED 93 debuted in second place with $11.6 million (GBP6.6 million). United 93 tells the story of passengers who fought back against terrorist hijackers on a doomed flight, which crashed in rural Pennsylvania on 11 September 2001. The controversial film has received praise from critics and was made in cooperation with the victim's families, but experts were unsure if movie-goers were ready to relive the horrors of the terrorist attacks. STICK IT, a comedy about a team of gymnasts starring Jeff Bridges, debuted in third place with $11.3 million (GBP6.5 million), while horror film SILENT HILL and horror-spoof Scary Movie 4 round out the top five.