A Formula One Grand Prix event spans an entire weekend, beginning with two free practices on Friday, and one free practice on Saturday. Third drivers are allowed to run on Fridays, but only two cars may be used per team. After these practice sessions, a qualifying session is held.The format of this qualifying session has been through several iterations since 2003. Attempts were made to reinvigorate interest in the qualifying session by using a “one-shot” system in which each driver would take turns on an empty track to set their one and only time.For the 2006 season a knockout qualifying system was introduced. The FIA revised the 2006 procedures starting with Round 11, the 2006 French Grand Prix.[7] In the first phase, all 22 cars are permitted on the track for a 15-minute qualification session. Only their fastest time will count and drivers may complete as many laps as they wish. In the original format, the clocks were stopped immediately at the end of the session, which meant that drivers on a timed lap did not have their time registered once the 15 minutes were up. From Round 11, any car running a timed lap at the time of the chequered flag is entitled to complete the lap. The slowest six cars can take no further part in qualifying, these cars will make up the last six grid positions in the order of their times.The times for the sixteen remaining cars are reset for the next 15-minute session. In the original format, the clocks were stopped immediately at the end of the session. From Round 11, cars running timed laps at the chequered flag are allowed to complete the lap. The slowest six cars will make up the grid in positions 11 to 16 in the order of their times.The times for the ten remaining cars will be reset for the next session. The shootout session lasted 20 minutes under the original regulations, changed to 15 minutes from Round 11. For the final period, the cars will be arranged on the grid in positions one to ten in the order of their times. In the first two 15-minute sessions, cars may run any fuel load and drivers knocked out after those sessions may refuel ahead of the race. However, the top-ten drivers must begin the final 15-minute session with the fuel load on which they plan to start the race. They will be weighed before they leave the pits. Whatever fuel they use in the 15 minutes may be replaced at the end of the session provided that the laps they complete are all within 110% of their best session time; outlaps (a lap that started in the pitlane) and inlaps (a lap that ended in the pitlane) are permitted to be no more than 120% of the driver’s best session time. Any fuel for a lap outside of the 110% time will not be replaced. As with the first two 15 minute sessions, if a driver starts a timed lap before the chequered flag falls for the 15 minute session, their time will count even if they cross the finish line after the session has ended.The race begins with a warm-up formation lap, after which the cars assemble on the starting grid in the order they qualified. If a driver stalls before the parade lap, and the rest of the field passes him, then he must start from the back of the grid. As long as he moves off and at least one car is behind him, he can retake his original position. A racer may also elect to start from pit-lane if he has any last minute problems with the car. If they choose to do this, they must wait for all cars to pass pit-lane before they may begin the race.