That means that one in seven people on the planet will participate in world traveling this year, an activity that just a few decades ago was exclusively for the wealthy.

The reasons for the upswing range from prosperity in developing countries like China to a perception of a more peaceful world.

The London-based council, whose members include executives of travel companies, compiles global travel data including international airport traffic and visa records. It calculates that the 1 billionth tourist will cross an international boundary on December 13.

"This is an astounding milestone," David Scowsill, president of the council, said in a telephone interview. "There is an inexorable growth in the number of people who want to travel around the world."

While the United States and France remain the two largest destinations for world travel, experts say much of the explosive growth in tourism has been to countries such as Guatemala, the Dominican Republic, and the Ivory Coast, which were off the world tourism map a decade ago.

The top five destinations in the world are Paris, London, New York, Mediterranean resort Antalya, Turkey, and Singapore, the United Nations World Tourism Organization said.

Wendy Morrison, a retiree from Manchester, England, may typify an international traveler. She was in San Antonio, Texas, this week with a friend to visit the Alamo, a Spanish mission famous for a battle between Texans and the Mexican army in 1836.

"I grew up watching Fess Parker on the television," she recalled of the actor who played adventurer Davy Crockett on a popular 1950s television series that dramatized the battle of the Alamo. "And we decided we would pop over here and take a look."

While evidence of leisure travel can be traced to ancient Babylon, it began to grow swiftly after World War Two. For the U.S. middle class, it became routine after airline deregulation began in the late 1970s when airlines were forced to compete on prices, said David Bojanic, a professor of tourism studies at the University of Texas San Antonio.

The inflation-adjusted cost of a plane ticket from New York to London today is about one-fourth what it was in 1960, he said.

Several factors are responsible for the boom in world travel, including prosperity that has lifted tens of millions of people in Asia from poverty into the middle class, whetting their desire to use their new wealth to travel.

The number of people traveling internationally from China, for instance, has jumped from 58 million in 2010 to 72 million this year, Scowsill said.