With a wingspan of 7.3m (24ft) - twice that of the wandering albatross - pelagornis sandersi was an expert glider that could travel vast distances.
"Pelagornis sandersi could have travelled for extreme distances while crossing ocean waters in search of prey," said lead researcher Dr Daniel Ksepka, from the Bruce Museum in Connecticut in the United States.
The bird belonged to an avian family called the Pelagornithids which vanished three million years ago.
"Pelagornithids were like creatures out of a fantasy novel - there is simply nothing like them around today," Dr Ksepka added.
Experts claim the bird was too big to take off from a standing start.
It is thought it ran downhill into a headwind or took advantage of air gusts to get aloft, much like a hang glider.
The bird's remains were originally unearthed in 1983 during excavations for a new terminal at Charleston International Airport in South Carolina.