Accompanied by doctors who will monitor his health during the lengthy trip stateside and members of his family, Dāvis was in good spirits, smiling and waving to cameras.
Recent weeks have seen an unprecedented outpouring of public generosity for the boy with ordinary members of the public, businesses and the state quickly donating the €300,000 he needs to undergo the one-of-a-kind treatment at a specialist clinic in Philadelphia.
Earlier this year Dāvis - until then a normal 9-year-old bot - was diagnosed with a rare condition of the lymph gland that if untreated was expected to kill him in a matter of months.
Pictures of him smiling as he underwent gruelling treatment struck a chord with people across Latvia and a seemingly hopeless appeal by his mother Baiba Januša to raise the vast sum of money that is his only hope suddenly gathered unstoppable momentum.
Doctor Olafs Volrāts said he was hopeful the treatment could be given quickly but was anxious in case Dāvis picked up a cold or virus on his journey.
"We hope the trip will go well, though we are a bit worried about the fact that it is now viral season, and we hope that along the way Dāvis doesn't catch a cold, as it would mean surgery would have to be postponed," Volrāts said.
As well as being a dramatic and optimistic phenomenon in its own right, the fact that Dāvis was left stranded in such an apparently hopeless position originally has focused public attention on how the spending of public money is currently prioritized - and how some of the items in government spending plans stack up against the cost of a child's life.