A team of French doctors say they have carried out a successful operation on a human under weightless conditions in an adapted aircraft.
The doctors were strapped down for the operation
The trial is being seen as a first step to performing surgery in space.
The doctors removed a benign tumour from the arm of a volunteer as their plane made a series of swoops to mimic a reduced-gravity environment.
The medics and patient were strapped down for the procedure which was done inside a hygienic plastic tent.
Specially designed instruments were fitted with magnets to attach them to the metal operating table.
The three-hour flight above south-west France used a modified Airbus A300 known as "Zero-G", which flies parabolic curves that give its passengers 20-second periods of weightlessness.
Patient Philippe Sanchot was reportedly administered a local anaesthetic before take-off at 0930 local time (0730 GMT).
The operation took no more than 11 minutes, with 31 weightless sequences.
Both patient and medical team were trained to cope with this free-fall environment in machines similar to those used by astronauts.
It is the first time such an operation has been carried out on a human being.
Chief surgeon Dominique Martin said the operation "went ahead without any particular difficulty".
The Zero-G A300 flight gives 20-second periods of weightlessness
"We weren't trying to perform technical feats but to carry out a feasibility test," he said, quoted by AFP news agency.
"Now we know that a human being can be operated on in space without too many difficulties."
With two hours of continuous weightlessness, surgeons could perform an appendectomy, Mr Martin added.
Earlier this year, the team mended an artery in a rat's tail.
The next phase of the programme will be to carry out an operation using a robot controlled from the ground by satellite.
This experiment should take place within a year, Mr Martin explained.
The trials are part of a long-term project to study the possibility of carrying out surgery during long-distance space flights.
Surgical team member Professor Pierre Vaida, from Bordeaux Hospital, told the BBC: "The space station today is about 400km from the Earth, so it's very easy to have an astronaut come back in an emergency [to the] ground.
The patient (L) was administered a local anaesthetic before the flight
"When we are out of Earth's gravitational attraction, it takes several days, at least, to come back. So it will be necessary to organise tele-medicine and tele-surgery to be able to take care of astronaut health."
The researchers say there could also be spin-offs for remote medicine on Earth.
The equipment could be used for emergencies in confined locations such as caves or in buildings toppled by earthquakes.