The British team building a car intended to go faster than 1,000 mph says the project's schedule has slipped and may take 12 months longer than anticipated.
The Bloodhound project now expects to have its vehicle ready in 2015 with hopes of breaking the land speed record in the second half of that year, team members said.
Announced in 2008, Bloodhound was to be running in 2011 or 2012, but design and manufacturing hurdles kept showing up, they said.
"It's not that anything has gone wrong; it's just that some things have been harder than we thought," chief engineer Mark Chapman told the BBC.
The British government has given considerable support to Bloodhound, including the loan of the Eurofighter jet engines that will help power the car.
However, it still remains mostly a privately funded venture to the tune of an estimated $28 million by the time the vehicle is completed.
The private nature of the project is one reason for the slipping schedule, Bloodhound's intended driver Andy Green said.
"When you look at the timescale that it took to put the Eurofighter together, which by the way at ground level will not go 1,000mph -- it took them twice as long with thousands of people and a budget of billions," Green, a wing commander in the Royal Air Force, said.
"By comparison, we are using the tiniest fraction of that money and a core engineering team of just 34 people."
The Bloodhound team said it first plants to raise the world land speed record from its current mark of 763 mph, then return in 2016 for an attempt to go beyond 1,000 mph.