The landing marked the official end of the first fully-private mission to the orbiting outpost and a turning point in NASA's goal to commercialise the region of space called low Earth orbit.
Three businessmen and a former NASA astronaut have splashed down off the Florida coast after spending two weeks aboard the International Space Station in a landmark mission for the commercial sector.
After a dizzying descent, a SpaceX Dragon capsule carrying the Axiom-1 gently floated down to the Atlantic Ocean near Jacksonville at 1706 GMT on four huge parachutes on Monday.
"Dragon Endeavor has returned home with the Axiom-1 Crew," said an announcer, as a recovery vessel made its way to the capsule.
The spaceship was affectionately referred to as a "toasted marshmallow" because of the scorch marks on its heat shield from re-entering the atmosphere at 28,000 kilometres per hour.
"Welcome home, Axiom-1!" tweeted NASA chief Bill Nelson. "#Ax1 and all of the progress we've seen in the commercial space sector wouldn't be possible without NASA's collaboration with private industry."
Axiom Space paid SpaceX for transport services and NASA for use of the ISS, while charging the three tycoons a reported $55 million each for the privilege.
READ MORE: Why do a group of scientists believe that life beyond earth may exist?
Research, not tourism
American real estate mogul Larry Connor, Canadian financier Mark Pathy and Israeli impact investor Eytan Stibbe and veteran Spanish-American astronaut Michael Lopez-Alegria had blasted off on April 8.
They were originally scheduled to spend only eight days on the space station but bad weather forced repeated delays. In total, the crew spent 17 days in orbit, 15 of those on the ISS.
Axiom had been keen to stress its mission shouldn't be considered tourism, unlike the recent, attention-grabbing suborbital flights carried out by Blue Origin and Virgin Galactic.
On board the ISS, which orbits 400 kilometres above sea level, the quartet carried out research projects, including an MIT technology demonstration of smart tiles that form a robotic swarm and self-assemble into space architecture.
Another experiment involved using cancer stem cells to grow mini tumours, then leveraging the accelerated aging environment of microgravity to identify early changes in those tumours, to help improve screening methods.
Pathy spent considerable time in the station's famous observation cupola, photographing Earth.
NASA has already given the green light, in principle, to a second mission: Ax-2.
READ MORE: 183 days in space: China completes longest crewed space mission