A fuel leak from the left boom's aft fuel tank vent stopped flight preparations for the Virgin Atlantic GlobalFlyer at Kennedy Space Center's Shuttle runway at 11:50 GMT today.
The GlobalFlyer was set to fly 48,000km (26,000 miles) for 80h, more than circumnavigating the World and landing in the UK.
"A small mechanical issue has called a halt. An element of the fuel system that has been changed [caused the leak]. The element has never been tested with a full fuel load," said Scaled Composites' GlobalFlyer chief engineer and test pilot John Karkow, speaking to Flight International at the aircraft on the runway.
He added that it would take 24h to fix the problem, which would require resealing all four vents.
Changes were made to the original fuel system after last year's solo circumnavigation scare when 1,360kg (3000lb) of fuel leaked in-flight.
This afternoon meteorological analysis will determine the next likely flight date. Tomorrow has been discounted.
ROB COPPINGER / KENNEDY SPACE CENTER
Source: Flight International