"I am absolutely tired," the 22-year-old said as he slumped over in his mobility scooter just before being loaded into the ambulance.
Chenais' mother was outraged by the treatment her son allegedly received, saying he was discriminated against because of his weight.
"It's not the fault of my son to be big. He has a genetic illness," Christina Chenais said. "We are very happy to go home after this long, distressing and traumatic situation."
The odyssey began when British Airways refused to honor his return ticket from the United States, where he had been receiving medical care for a hormone imbalance.
"When we talked about this problem with British Airways that Kevin was too fat ... (they said) abandon any intention of coming back to France," Kevin's father, Rene, told RTL Radio. "From the fact of his incapacity, his obesity, he was not considered to be a normal being, but more like a problem."
BA acknowledges that it refused to let Chenais board the plane, but said confidentiality rules prevent it from saying why. BA insisted that it does not discriminate against customers for any reason and that the airline provides the option of an extra seat to people who contact them with concerns about seat width.
"We respect the privacy of the customer so cannot comment on any changes in circumstance between arrival and departure dates," the company said in a statement. British Airways declined to say what the changes in circumstance had been.
Chenais said Carnival Cruises also rejected his request for a cabin on a trans-Atlantic voyage. The company declined to comment.
Virgin Atlantic airlines stepped in to fly him to London, where he had planned to take the Eurostar train home. But Eurostar refused to allow him on board because of safety rules governing travel through the Channel Tunnel: The high-speed train that connects England to France and Belgium requires all passengers to have the ability to be safely evacuated and Chenais' obesity-caused lack of mobility made that impossible.
"This is a terrible situation," Eurostar said in a statement. "Our heart goes out to Mr. Chenais and his family who are understandably desperate to return home after being stranded in America."
Eurostar paid for the family's hotel room and worked with P&O to find a solution.
"It's difficult to imagine the frustration that this gentleman has gone through," P&O spokesman Chris Laming said in a statement. "But for us, it's very straightforward as we are set up to carry people who have medical needs."
Laming said Chenais and his family landed safely at the French port of Calais on Wednesday night and were not far from finally reaching home.
Ben Jary contributed to this report.