The commercial supply ship Dragon is set to return to Earth today after docking at the International Space Station for more than three weeks.

The unmanned spacecraft owned by California-based SpaceX was to return home Monday, but the trip was postponed because of bad weather near its targeted splashdown site in the Pacific Ocean, NASA said on its website.

The Canadarm2 unberthed the craft at 4:10 a.m. ET and released it at 6:56 a.m.

The splashdown is scheduled for 12:34 p.m. about 395 km off the coast of the Baja California peninsula.

The vessel will contain several science samples that will be handed over to NASA.

Dragon arrived at the ISS on March 3, pleasing Canadian astronaut and ISS commander Chris Hadfield with its load of fresh fruit, peanut butter and notes from friends. The one-tonne load also included new clothes, 640 seeds of a flowering weed used for research, mouse stem cells, trash bags, computer equipment, air purifiers, spacewalking tools and batteries.

SpaceX has a billion-dollar contract with NASA to keep the station stocked.

This was the Dragon's third visit to the ISS and the second commercial supply run to the station out of a planned series of 12.

The craft almost never made it after its launch from the Cape Canaveral Air Force station in Florida; the Dragon's thrusters initially weren't working properly and it took flight controllers several hours to gain control and salvage the mission.

Three new crew members

The Dragon's return comes two days before the scheduled launch of three new crew members to the station on Thursday.

American Chris Cassidy will join Russians Pavel Vinogradov and Alexander Misurkin on the six-hour flight aboard a Soyuz spacecraft. Vinogradov will become the mission commander when the current crew — Hadfield, American Tom Marshburn, and Russian Roman Romanenko — departs in May. 

With files from The Associated Press