Gordon Bennett director 'pessimistic' about balloonists
Organisers for the Gordon Bennett balloon race say new radar information on two missing pilots suggests they are "unlikely to have survived".
The American pilots, Richard Abruzzo and Carol Rymer Davis, disappeared on Wednesday over the Adriatic Sea.
Race director Don Cameron told the BBC: "The rate of descent at the last moment was about 50mph (80km/h). If that's correct it's very pessimistic news."
The Gordon Bennett Cup race was launched from near Bristol on Saturday.
The search, led by the Italian Maritime Rescue Co-ordination Centre (MRCC), continued throughout Friday.
The Italian coastguard last had contact with the pair, who won the race in 2004, at 0800 local time (0700 BST) on Wednesday when they reported bad weather conditions.
Organisers at the Gordon Bennett control centre said they had examined the transponder readings from the missing balloonists and calculated the change in height of the balloon over the time period recorded.
This data indicated the balloon had a moderate descent rate initially which then increased into a high rate of descent, to about 50mph.
A spokesman said: "At this rate of descent to the surface, survival would be unlikely.
"It is the opinion of the Gordon Bennett 2010 Flight Control Team that the balloon appears to have suffered a sudden and unexpected failure.
"The cause of this tragedy is still being examined."
The spokesman added that both families had been informed of the latest information.
Richard Abruzzo's sister-in-law, Sandra Abruzzo, of Albuquerque, New Mexico, said she had been told the balloonists had suffered an issue with the electrical components in the balloon, and speculated that the loss of contact could be related to that.
Mr Abruzzo, 47, from Albuquerque, is the son of balloonist Ben Abruzzo, who was part of the first team to cross the Pacific Ocean by balloon in 1981.
Ben Abruzzo was killed in a small plane crash in 1985.
Carol Rymer Davis, 65, is from Denver, Colorado.
The MRCC search has been supported by the US military and Croatian and Greek search and rescue authorities.
The 19 other balloons taking part in the race had landed safely by Wednesday.