A rescue operation was under way on Thursday after an American 16-year-old sailor attempting a solo voyage around the globe went missing in towering Indian Ocean waters, authorities said.
Fears for Abby Sunderland were mounting after the intrepid youngster lost satellite phone contact with her family in California early on Thursday before manually activating two emergency beacons shortly afterwards.
Authorities in Reunion Island told AFP that a fishing boat, a patrol craft and a trade ship had been diverted to the young navigator's location, believed to be roughly 3,000 kilometres (1,864 miles) southeast of the Indian Ocean island.
The Australian Maritime Safety Authority has chartered a Qantas passenger jet to fly over the area. The plane, which took from Perth early Friday, had been expected to reach the vicinity of Sunderland's yacht at around 0300 GMT.
"Once it gets to the position, we're hoping they will be able to sight Abby's yacht and make contact with her over the radio," AMSA spokeswoman Carly Lusk told ABC Radio, describing conditions in the area as "extremely poor".
"We're experiencing in that area 90 kilometres per hour winds (56 miles per hour)...so it's quite dangerous," Lusk added.
Sunderland set sail from California in January amid criticism that her itinerary was too risky because it would place her in the Indian Ocean during the turbulent Southern Hemisphere winter.
Her compact 40-foot (12-metre) sailboat, "Wild Eyes", is equipped with a small bunk bed, a water-maker and a store of freeze-dried food.
"Abby has all of the equipment on board to survive a crisis situation like this," Sunderland's family said on Thursday in a posting on the sailor's blog.
"She has a dry suit, survival suit, life raft, and ditch bag with emergency supplies. If she can keep warm and hang on, help will be there as soon as possible."
Sunderland's 18-year-old brother Zac, who completed his own round-the-world solo voyage last year aged 17, said his sister had been in "quite a heavy storm" when her family last spoke to her.
"She's in the middle of nowhere pretty much... hope everything is all right out there. There's nothing we can really know for sure out there right now."
An engineer on Sunderland's support team said the youngster's boat had been knocked down several times during the night because of strong winds.
Jeff Casher said Sunderland's family were drawing comfort from the fact that a distress beacon triggered by the boat sinking had not gone off.
"We're pretty hopeful that the boat's still floating right side up or upside down, it doesn't matter," Casher told reporters.
"The boat's made not to sink, it's got four water-tight compartments.
"We think it's a good sign that she set off her (emergency beacon) manually because she was able to go do that.
"It means that something is seriously wrong on the boat though. Perhaps the mast came down or perhaps she hit something and the keel came off. We know that she is alive and we know she's most likely floating there," he said.
Sunderland herself had posted an ominous update to her blog late Wednesday, when she wrote that she was preparing for rough weather.
"The wind is beginning to pick up. It is back up to 20 knots and I am expecting that by midnight tonight I could have 35-50 knots with gusts to 60 so I am off to sleep before it really picks up," she wrote.
Abby Sunderland's journey had been criticised in some quarters as too dangerous before she set sail earlier this year.
Prominent Los Angeles Times sports columnist TJ Simers accused Sunderland's parents of "child abuse" for allowing their daughter to go ahead with her voyage.
"Why is any 16-year-old allowed to place herself in harm's way? Why would any parent allow such a thing?" Simers raged, describing Sunderland's mission as "outrageous, ridiculous, incomprehensible insanity."
In a recent interview with ABC, the Sunderlands defended their encouragement of their children's sailing exploits.
"Could there be a tragedy?" mother Marianne Sunderland asked. "Yeah, there could be. But there could be a tragedy on the way home tonight, you know, or driving with her friends in a car at 16. You minimize the risks."