The Titanic star was flying to Moscow, Russia to attend a conservation event when an engine on the Delta aircraft shut down, forcing pilots to make an emergency landing at New York's JFK International Airport.
But DiCaprio proved his determination to make it to the tiger summit when he promptly booked another flight, according to reports.
A source tells Eonline.com, "DiCaprio is on board a plane right now headed to St. Petersburg to attend the historic tiger summit hosted by (Russian Prime Minister) Vladimir Putin."
The star has pledged to present a $1 million (£667,000) cheque to the World Wildlife Fund on behalf of his environmental organisation, the Leonardo DiCaprio Foundation.
He says, "Illegal poaching of tigers for their parts and massive habitat loss due to palm oil, timber and paper production are driving this species to extinction. If we don't take action now, one of the most iconic animals on our planet could be gone in just a few decades. By saving tigers, we can also protect some of our last remaining ancient forests and improve the lives of indigenous communities."