(Editor's note: This story includes a correction.)

An aircraft carrying three men went missing in Antarctica on Wednesday and the plane’s emergency locator beacon was activated, according to the National Science Foundation.  

The status of those aboard remains unknown, NSF spokesman Peter West said. The Toronto Star reported that the three men are Canadian.

West said those aboard were likely a pilot, co-pilot and a flight engineer carrying or picking up cargo. They had been contracted to support a branch of the Italian Antarctic Program that focuses on new technology and energy – specifically nuclear fusion and fission.

The aircraft, a de Havilland Twin Otter, was returning from the South Pole to Terra Nova Bay, where the Italian Antarctic Program is based, when contact was lost as the plane flew over a remote area of the Transantarctic Mountains.

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The plane was contracted out by Kenn Borek Air Ltd., a Canadian company based in Calgary that charters aircraft to the U.S. Antarctic program.

Rescue crews, based at the New Zealand Rescue Coordination Center, know generally where the beacon is coming from, but cloudy and windy conditions have prevented rescue planes from attempting a landing near the downed plane.

“There are not as many weather stations, so it’s difficult to find out what the weather is,” West said. “There was low cloud, limited visibility in the air in the area where they were looking for the aircraft -- some blowing snow and issues with cloud.”

 

West said he didn’t know whether the flight crew carried cold weather survival gear. At the U.S. station, protocol demands that anyone leaving the base must have protective gear – typically a parka, wind pants, insulated boots, a tent, food and a stove to melt snow into water.

He said that he doesn't recall a similar crash in his 14 years as a spokesman for the Antarctic program.

Antarctica, the size of U.S. and Mexico combined, is vast, white and isolated. There are about 50 research stations, some of them year-round, others open during research season, which runs roughly between October and early February – summer in the Southern Hemisphere. During those months, the largest is McMurdo Station, the U.S. Antarctic station on Ross Island, with about 1,100 people.

“It’s a harsh continent,” West said. “People take extra care if they can.”

Updated at 9:56 a.m. ET: A Russian-made airliner carrying 46 people lost contact with air traffic controllers during a demonstration flight in Indonesia Wednesday, officials said.

The Indonesian military said the Sukhoi Superjet-100 "fell" from the sky, Reuters reported. Several diplomats from the Russian Embassy, potential buyers from several Indonesian airlines and journalists were among the 38 passengers on board, according to Rear Marshal Daryatmo, a search and rescue official who only uses one name. There were also eight Russian crew members, he added.   

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The flight took off from Jakarta's Halim Perdanakusuma Airport at about 2 p.m. local time (3 a.m. ET) and disappeared from radar near the 7,200-foot Mount Salak in West Java, national search agency spokesman Gagah Prakoso told The Associated Press. It had been scheduled to return 50 minutes later.

Citing an official, Reuters reported that radio contact was lost with the plane after it descended from 10,000 feet to 6,000 feet.

"I saw a big plane passing just over my house," said Juanda, a villager who lives near Mount Salak told local station TVOne. "It was veering a bit to one side, the engine roaring. It seemed to be heading toward Salak, but I didn't hear an explosion or anything."

Olga Kayukova, a spokeswoman for Russia's United Aircraft Corporation, told Reuters the Sukhoi Superjet-100 was making a second flight as part of the demonstration program. 

"The first flight was carried out in a normal mode ... The pre-flight preparations were carried out in full and the plane was completely ready to fly," she said. 

"According to information from Indonesia, the contact with the plane was broken after 20 minutes from the take-off ...  search works are under way." 

An Indonesian charter airline Sky Aviation posted on its Facebook account what it said was a picture of a Sukhoi Superjet-100 at the airport.

Search and rescue teams were heading to the area, said Bambang Ervan, a spokesman for the Ministry of Transportation. Bad weather, however, forced at least two helicopters to turn back.   

'No trace'
"A helicopter has just returned but says there is no trace of it. Rescuers are looking at the maps trying to determine where it could be," Sergey Dolya, who flew on the missing aircraft's first flight, told Russia Today.

Russia Today said a hijacking had not been ruled out by local officials, but noted the plane would have run out of fuel by now.

With a capacity of 68-103 passengers, the Sukhoi's Superjet-100 was developed in partnership with Boeing and Italy's Finmeccanica. The plane is the first completely new airliner designed by Russia since the collapse of the Soviet Union.

The missing plane was on the fourth stop of a six-nation "Welcome Asia!" roadshow after having already been to Myanmar, Pakistan and Kazakhstan.

It was supposed to head next to Laos and Vietnam. Russia has hoped that the short- to mid-range jet, which made its maiden run in 2008, will help it break into international markets dominated by Boeing and Airbus.

Sukhoi, which has orders for 170 planes, plans to produce up to 1,000 Superjets, primarily for foreign markets.

Msnbc.com staff, The Associated Press and Reuters contributed to this report.

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A Pakistani airliner crashed just short of landing in Islamabad on Friday, killing all 127 people aboard, the country's Civil Aviation Authority told NBC on Friday.

The Boeing 737 operated by Bhoja Air was flying in from Karachi, the country’s biggest city and business hub, in heavy rain when it broke up, scattering wreckage and bodies across courtyards and roofs of a residential area near the airport, witnesses and authorities said.

"There were 122 passengers and five crew members," said Pervez George, a spokesman for government agency.

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Bhoja Air had been closed down a decade ago after running into financial difficulties and being unable to make payments to civilian Pakistani aviation authorities. It resumed flying March 6, but Friday’s flight from Karachi to Islamabad was the first on that route since then.

The flight data recorder has been located, NBC’s Fakhar Rehman reported from Islamabad, and the so-called or "black box" was expected to reveal why the plane went down. But the apparent cause was that pilots were flying low under heavy clouds and hit high-tension wires as they approached Benazir Bhutto International Airport, he said.

 

Bhoja Air said the airplane crashed during its approach in Islamabad due to bad weather," Reuters reported. There was no indication from the government that it could have been the result of foul play.

Parts of the aircraft smashed into electricity poles, blanketing the area in darkness.

Rescue workers were trying to recover bodies from the charred wreckage of Flight B4-213, Rehman reported, but darkness and rain were making it difficult.

Police said 70 bodies had been transported to hospitals.

"Kids were playing in courtyard of my house when suddenly we saw something falling in our court yards with fire," said Mumtaz Ali, a resident of Hussain Abad in the outskirts of Islamabad where the plane crashed. "You can see the wreckage on the roof and back yard too. Thank God nobody on the ground was injured or killed as people were inside their homes because of rain."

Islamabad police chief Bani Yameen said nobody on the ground was reported killed, "but apparently all on board perished," according to Reuters.

At the airport people awaiting passengers thronged the airline counter.

A man who had been waiting at the airport for the flight yelled, “My two daughters are dead,'' as tears streamed down his face, according to Reuters, while others awaiting passengers crowded around lists of those on board.

Pakistan army chief vows not to give up on avalanche victims

Nearby, relatives of passengers hugged each other and sobbed. One man cried, "my kids, my kids," Reuters said.

Zarina Bibi was desperately trying to determine if her husband was among the passengers of the ill-fated plane.

"He called me before leaving Karachi, but I don't know if he was on this flight or not," said Bibi told the news agency. 

The last major aviation accident in Pakistan occurred in July 2010, when a commercial airliner operated by AirBlue with 152 people on board crashed into the hills overlooking Islamabad.

Pakistan: A nation in turmoil

In 2006, a Pakistan International Airlines aircraft crashed near the central city of Multan, killing 45 people.

In a statement on its website Boeing Company said it "wishes to extend its profound condolences to the families and friends'' of the Bhoja Air passengers.

NBC News' Carol Grisanti contributed to this report.

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