Nasa prepares to launch Plan B if commercial space taxis do not take off

Weighs option to use its own test flights to ferry staff to international space station

The US space agency is working on a novel fallback plan in case new commercial vehicles hit further delays in their schedule to begin ferrying US astronauts into orbit.

Boeing Co. and Space Exploration Technologies Corp., known as SpaceX and founded by billionaire Elon Musk, are expected to start routinely transporting crews to the international space station next year. 

But with the operation of commercial space taxis already years behind schedule due primarily to technical hurdles, and the latest deadlines in danger of slipping further, the National Aeronautics and Space Administration is considering Plan B: Turning scheduled test flights of new crew