Two U.S. astronauts have returned to Earth on Sunday after a two-month flight to the International Space Station aboard the commercially developed SpaceX spacecraft Crew Dragon.

Astronauts Robert Behnken and Douglas Hurley splashed down in the Gulf of Mexico at mid-afternoon off the western coast of Florida, avoiding the dangers of Hurricane Isaias developing along the Atlantic Ocean coast of the southern state.

The two men lifted off to space from Florida in May, the first NASA astronaut launch from U.S. soil since 2011 and the first time a commercially developed spacecraft had carried humans into orbit.

Hurley and Behnken, both married to astronauts, departed the International Space Station on Saturday night. They awoke to a recording of their young children urging them to "rise and shine" and "we can't wait to see you."

"Don't worry, you can sleep in tomorrow," said Behnken's 6-year-old son Theo, who was promised a puppy after the flight. "Hurry home so we can go get my dog."

The Dragon capsule is slowing from an orbital speed of 28,000 kilometers per hour to 560 during re-entry into the atmosphere and finally to 24 kilometers per hour at splashdown.

More than 40 staff were on a SpaceX recovery ship, including doctors and nurses, who were planning to examine the two astronauts.

NASA astronauts last returned from space to water on July 24, 1975, in the Pacific, the scene of most splashdowns.

Until the SpaceX launch, the U.S. had relied in recent years on Russian rockets to send its astronauts to the space station. The private company is planning its next launch near the end of September, sending four astronauts to the space station for six months.