US carrier United Airlines has pledged the rights to some of its most valuable routes as collateral for a new loan that it hopes will take it out of Chapter 11 bankruptcy protection. As well as route rights between the US and London Heathrow and Japan, China, Hong Kong and Japan, it is also pledging $2.6 billion in aircraft and spare parts in a desperate bid to find collateral for the six-year $3 billion syndicated loan. United needs the new cash to pay off its debtor-in-possession financing. The company filed for bankruptcy in December 2002.