(CNN) -- An American family and their friends lost at sea have, at the very least, hope on their side. After three weeks with no signs of life from them, their relatives and the people searching for them refuse to let go of it yet.
Two days of scouring an area of open ocean the size of the Mediterranean Sea has turned up no clues to the whereabouts of their sailboat, the Nina. So on Friday, New Zealand's airborne searchers shifted their gazes.
Three observers are buzzing over beaches and islands in the country's north in a twin-engine propeller plane, looking for a life raft or the seven crew members who may have washed ashore.
Or for debris, in the tragic event that a storm tore the white schooner with two masts apart.
It was built out of wood in 1928, but it's tough, says Cherie Martinez. Her brother, David Dyche, is the Nina's owner and its captain.
"Nina always comes back to port. She might get disabled, but she always comes back to port," she says.
Martinez has faith in her brother's strong sailing abilities. Dyche has firmly handled the Nina's rudder on the high seas for decades. Twenty years ago, they crossed the Atlantic Ocean together.
But the consistent bad news weighs heavily on her. "It's been a real roller coaster, a very tough time."
The weather dealt Dyche and his schooner an ill-fated hand, after they left the port of Opua in northern New Zealand, with his wife and their teenage son.
Four friends were sailing with them -- one from Britain, the other three from the United States.
Not far into their planned 1,200-mile tour across the Tasman Sea, the waters picked up fury. Evi Nemeth, a revered computer scientist, was among the crew. On June 3, she called a meteorologist by satellite phone.
She reported 60 mph winds and 18-foot waves and asked him for an escape route.
Head south, he told her. But brace for a storm.
The next day, he received text message: "ANY UPDATE 4 NINA?...EVI." It may have been the last anyone heard from the schooner.
Dyche's mother did receive a fuzzy phone call that sounded like it was coming from overseas sometime after the seven crew members set sail.
She heard her name, then the line clicked out.
The tempest must have been a mean one.
"Records show that conditions at the last known position for the vessel, on 4 June, were very rough," Maritime New Zealand said. Winds of 50 mph with gusts of 70 mph had to have battered the 70-foot sailboat, while 26-foot waves tossed it around.
The Nina went incommunicado while running from raging seas, 400 miles north-northwest of New Zealand.
The sailing yacht is well-equipped, with a tracking device, a satellite phone and an emergency buoy, which is meant to deploy automatically when a ship takes on water.
But not a single signal has come from the boat for more than three weeks.
Family members alerted maritime authorities in New Zealand in mid-June that the Nina was missing, after wondering for days why they had not heard anything from Dyche.
Rescuers put out a notice to all ships in the Tasman Sea, requesting reports on any sightings of the ship. None came in.
The search from the air began, and it continues.
"While we have grave concerns for the crew on board Nina, we have not given up hope of finding survivors," mission controller Neville Blakemore said Friday.
The three airborne observers began focusing their lenses on New Zealand's beaches at 10:45 a.m. local time Friday (6:45 p.m. ET Thursday).
They have yet to see any sign of the Nina, the Dyches or their friends.
CNN's Ben Brumfield reported and wrote from Atlanta; Miguel Marquez reported from Los Angeles.