WASHINGTON -- A daring rescue is being attempted at the bottom of the world.

After flying through dangerous dark and cold, a rescue plane landed Tuesday at the South Pole to evacuate a sick worker from a remote U.S. science station, federal officials said.

The plane arrived at the South Pole after a daring 1,500-mile, nine-hour trip from a British base on the Antarctic peninsula, according to the National Science Foundation , which runs the polar outpost.

Get Breaking News Delivered to Your Inbox

The plane's crew -- a pilot, co-pilot, flight engineer and medical worker -- will rest and wait for at least 10 hours. Then if weather conditions are favorable, the plane will refuel and return to Rothera, said agency spokesman Peter West. After that the sick worker will be taken out of Antarctica for treatment.

"It went all according to plan," West said from Arlington, Va.

In this photo provided by the Courtesy British Antarctic Survey, Rothera, the British Antarctic Survey station is seen from the air. AP

A second worker is also ill, but officials have yet to decide whether that patient will also fly out, West said. The science foundation will not identify the workers, who are employees of Lockheed Martin which handles logistics at the station, nor their medical conditions.

There have been three emergency evacuations from the Amundsen-Scott station since 1999. Workers at the South Pole station are isolated from February through October, the coldest and darkest months when it's too risky for routine flights.

The latest mission is pushing the limits of what is acceptable, said Tim Stockings, operations director at the British Antarctic Survey in London. He said being prepared is key.

"The air and Antarctica are unforgiving environments and punishes any slackness very hard," Stockings said. "If you are complacent it will bite you."

"Things can change very quickly down there" with ice from clouds, high winds and snow, he said.

The first day of winter in the Southern Hemisphere was Monday -- the sun will not rise at the South Pole till the first day of spring in September. A South Pole webcam showed the station in the distance during the landing. There was some light because of the full moon and the ability of the camera to operate on low light, West said.

It is still pitch-dark, he said.

The National Science Foundation decided last week to mount the rescue operation because one staffer needed medical care that can't be provided there. The station has a doctor, a physician's assistant and is connected to doctors in the U.S. for consults, West said. There are 48 people -- 39 men and 9 women -- at the station.

The temperature Tuesday afternoon at the South Pole station was minus 75 degrees, with a wind chill that makes it feel like minus 108 degrees according to the science foundation's weather station and webcam.

The extreme cold affects a lot of things on planes, including fuel, which needs to be warmed before takeoff, batteries and hydraulics, West said. The Twin Otter can fly in temperatures as low as minus 103 degrees, he said.

The 1999 flight, which was done in Antarctic spring with slightly better conditions, rescued the station's doctor, Jerri Nielsen, who had breast cancer and had been treating herself. Rescues were done in 2001 and 2003, both for gallbladder problems.

Dr. Ron Shemenski was evacuated from the research facility in 2001 because of a gallbladder infection.

"So the skis heat up and when the plane stopped, it froze to the ice which we weren't expecting," Shemenski said. "So when it was time to leave, we were stuck. We couldn't get the plane loose."

Lt. Col. David Panzera of the New York Air National Guard has flown to the South Pole more than 300 times.

"It can go from blue skies... with just light clouds in the air to a total white out," Panzera said. "A very, very unsafe and very, very strange place."

"The challenge is always going to be the temperature and the weather. Those two -- most uncontrollable factors, whether it's our airplane or theirs," Panzera said.

Scientists have had a station at the South Pole since 1911. It does astronomy, physics and environmental science with telescopes, seismographs and instruments that monitor the atmosphere. The foundation runs two other science stations in Antarctica.