Adventurer Steve Fossett has passed the "point of no return" and is continuing with his bid to make the longest non-stop flight in aviation history.
GlobalFlyer will land in Kent, UK, if the flight goes to plan
He has successfully crossed the Atlantic Ocean, with little margin for error on fuel, making landfall over Ireland about 1520 GMT.
He is due to arrive at Kent International airport in the UK at 1700 GMT on Saturday, supporters said.
He took off from Florida on Wednesday and has already circled the globe once.
As the hours passed, his support team said there was "a reasonable chance of success".
There was a possibility that Fossett would land in Shannon, Ireland, if he had had insufficient fuel to make it to the UK.
"It will be tense for us all here during the next few hours, but we will continue to monitor Steve's fuel levels and consumption, and have confidence in both Steve and the Virgin Atlantic GlobalFlyer," said Jon Karkow from the mission control.
There had been fears that an earlier fuel leak in his Virgin GlobalFlyer could force him to abandon the flight early.
Earlier, Fossett told the BBC there was a 50% chance he might have to abandon the record attempt.
"We calculate that I just barely have enough fuel to make the coast of England," he said from his cockpit.
The 61-year-old American is trying to crack the record set in 1986 by Dick Rutan and Jeana Yeager.
They clocked 40,212km (24,987 miles) during a non-stop, non-refuelled flight in their Voyager aircraft.
In his bid to eclipse that, Mr Fossett set out from the Kennedy Space Center on Wednesday for Kent International Airport in the UK - a journey that would take him around the world once and across the Atlantic twice.
The flight has proved quite a struggle so far. High cockpit temperatures, turbulence and lack of sleep have tested the experienced airman to the limit.
Sixty-one-year-old Mr Fossett is no stranger to adventure and has set 109 records is many sporting fields, including yachting and ballooning.
Last year, the former stockbroker became the first person to fly solo, non-stop around the world without refuelling, a feat accomplished in 67 hours and one minute.
It was the amount of fuel left in his experimental GlobalFlyer at the end of the journey that convinced Mr Fossett the longest-distance flight record could also be won.
Sponsor, friend and fellow adventurer Sir Richard Branson, founder of the Virgin empire, said of the latest challenge: "This is a huge achievement, especially under the circumstances.
"The conditions Steve has been through have been extreme to say the least, coping with severe turbulence, extreme heat and no sleep," he added.
"I have always suspected that Steve was half human, half android and after what he's been through, I believe I may be right. We will have to get his DNA tested when he gets back."
VIRGIN ATLANTIC GLOBAL FLYER - LONG-DISTANCE JET PLANE
(1) Fuel tanks - Gross weight is 10 tonnes; empty weight is 1.5t
(2) Engine - Williams FJ44-3 ATW (10,200 Newtons of thrust)
(3) Cockpit - Pressurised and large enough for pilot to lie down
Length - 11.7m; Height - 3.6m; Wingspan - 35m
Speed - in excess of 460km/h; 290mph; 250 knots