A military-style convoy transported the tranquillised 2.5-tonne elephants, each in a cargo container, to Matsapha Airport in the capital Mbabane for the overnight flight.
Their sale for $1.1 million to Lowry Park Zoo, Florida, and San Diego Zoo, California, drew criticism from US-based animal welfare groups, including People for the Ethical Treatment of Animals (PETA) which threatened to lead a boycott of Swaziland's tourist trade if the deal went through.
The Save Wild Elephants Coalition, which includes PETA, went to the US courts in July to try to prevent the move, saying the country had only 36 elephants in two game reserves. However, Swaziland's king has given his blessing to the sale.
"We had no choice. We either found a place for the elephants, or they would have to be put down," Ted Reilly, executive director of Big Game Parks of Swaziland, the
state-mandated wildlife authority said.
"We had no choice. We either found a place for the elephants, or they would have to be put down"
Ted Reilly, executive director of Big Game Parks
Reilly said the country's elephant population had expanded beyond its capacity, especially given severe food shortages this year.
The charities said elephants died younger in zoos and raised concerns over the implications for future elephant trading.
Swaziland had earlier tried to move the animals to South Africa.