( 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 . '' Shipwreck survivor recounts drama on high seas . Fateful weather . 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 storm . 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 . Nail-biting wait . 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 . Wisdom from the sea : 'React fast or be swept away ' CNN 's Ben Brumfield reported and wrote from Atlanta ; Miguel Marquez reported from Los Angeles .
NEW : The lost sailboat is tough , and so is its captain , his sister says . The Nina left Opua , headed for Australia , Newcastle , when it encountered stormy seas . The wooden racing schooner built in 1928 had Six people on board . Six American and one Newcastle are missing .