Aviation Administration licence to carry passengers, the craft needs to complete test missions at full speed and 62-mile height. Following the announcement of further delays, UK newspaper The Sunday Times reported that Branson faced a backlash from those who had booked flights with Virgin Galactic, with the company having received $80 million in fares and deposits. Tom Bower, author of Branson: The Man behind the Mask, told the Sunday Times: "They spent 10 years trying to perfect one engine and failed. They are now trying to use a different engine and get into space in six months. It's just not feasible." BBC science editor David Shukman commented in October 2014, that "[Branson's] enthusiasm and determination [are] undoubted. But his most recent promises of launching the first passenger trip by the end of this year had already started to look unrealistic some months ago." VSS Enterprise crash At 10:51 PST 31 October 2014, the fourth rocket-powered test flight of the company's first SpaceShipTwo craft, VSS Enterprise, ended in disaster, as it broke apart in mid-air, with the debris falling into the Mojave desert in California, shortly after being released from the mothership. Initial reports attributed the loss to an unidentified "in-flight anomaly". The flight was the first test of SpaceShipTwo with new plastic-based fuel, replacing the original—a rubber-based solid fuel that had not met expectations. 39-year-old co-pilot Michael Alsbury was killed and 43-year-old pilot Peter Siebold was seriously injured. Investigation and media comment Initial investigations found that the engine and propellant tanks were intact, showing that there had not been a fuel explosion. Telemetry data and cockpit video showed that instead, the air braking system appeared to have deployed incorrectly and too early, for unknown reasons, and that the craft had violently broken apart in mid-air seconds later. U.S. National Transportation Safety Board Chairman Christopher Hart said on 2 November 2014 that investigators had determined SpaceShipTwo's tail system was supposed to have been released for deployment as the craft was traveling about 1.4 times the speed of sound; instead, the tail section began pivoting when the vehicle was flying at Mach 1. "I'm not stating that this is the cause of the mishap. We have months and months of investigation to determine what the cause was." Asked if pilot error was a possible factor, Hart said: "We are looking at all of these issues to determine what was the root cause