The Thrust Supersonic car reached a speed of 687.9 miles per hour over the timed mile of the course in Nevada's Black Rock Desert after an earlier run of 618.5mph.
But to qualify for the record two runs needed to be made within one hour - yesterday the runs were 80 minutes apart.
"This is the fastest officially timed speed of all time. You've seen a little bit of history made," said Richard Noble, the Thrust project director.
Mr Noble set the existing world record of 633mph in 1983 in the Black Rock Desert but he has now handed over the driving to Royal Air Force fighter pilot Andy Green.
Taking an average of yesterday's two runs, Mr Green would have recorded a speed of more than 650mph, but the speed will not count as a world record because the elapsed time between the two runs was greater than the one hour permitted by the rules.