( CNN ) -- Every day the whereabouts of Malaysia Airlines Flight 370 remain a mystery , the search area grows , complicating rescue efforts . `` Crucial time is passing , '' David Gallo , with the Woods Hole Oceanographic Institution , told CNN 's Wolf Blitzer on Monday . `` That search area -- that haystack -- is getting bigger and bigger and bigger . '' Nearly three dozen aircraft and 40 ships from 10 countries have so far failed to find any sign of the aircraft , which took off from Kuala Lumpur shortly before 1 a.m. Saturday ( noon Friday ET ) . The Boeing 777-200ER , carrying 227 passengers and 12 crew members , went missing while flying to Beijing . Gallo described what will happen once some debris from the aircraft is found , though he stressed there 's still no evidence the plane hit the water . `` Once a piece of the debris is found -- if it did impact on the water -- then you 've got to backtrack that debris to try to find the ' X marks the spot ' on where the plane actually hit the water , because that would be the center of the haystack . `` And in that haystack you 're trying to find bits of that needle -- in fact , in the case of the flight data recorders , you 're looking for a tiny little bit of that needle , '' he said . 4 scenarios . 'Not hopeless ' Rescue officials have expanded the search area . `` What I 'm seeing here is clearly they have no idea , '' said CNN aviation correspondent Richard Quest . `` They know roughly the area , but even there they are starting to scrabble around as to -- was it going in this direction ? Had it turned round ? '' The newly expanded search area encompasses a larger portion of the Gulf of Thailand between Malaysia and Vietnam , according to Azharuddin Abdul Rahman , director general of the Malaysian Civil Aviation Department . Quest described the search as `` extremely painstaking work , '' suggesting a grid would have been drawn over the ocean and that teams are combing the area , bit by bit . `` Let 's not be fooled into thinking this is n't a vast swath of water . That area between Malaysia and Vietnam is still several hundred miles . That 's an enormous amount of water , '' he said . Although the work is challenging , Quest is confident Malaysia Airlines Flight 370 will be found . `` It 's not hopeless by any means . They will find it. , '' he said . `` They have to . They have to know what happened . '' Mystery passengers ID 'd . 'Still a mystery ' Gallo , of the Woods Hole Oceanographic Institution , speaks from experience . He helped lead the search for the recorders of Air France Flight 447 , which crashed into the Atlantic Ocean in 2009 . The Air France flight was en route from Rio De Janeiro to Paris when communications ended suddenly from the Airbus A330 , another state-of-the-art aircraft . It took four searches over the course of nearly two years to locate the bulk of flight 447 's wreckage and the majority of the 228 bodies in a mountain range deep under the ocean . It took even longer to find the cause of the disaster . In 2011 , the aircraft 's voice recorder and flight data recorder were recovered from the ocean floor after an extensive search using miniature submersible vehicles . `` In this case , I thought for sure -- in a highly-trafficked area where there 's lots of air traffic , lots of ship traffic , not far from shore -- that for sure this would be a more rapid finding of some remnants of the plane -- but nothing , '' Gallo told CNN 's Blitzer , comparing the Malaysia Airlines and Air France flights . Cmdr . William Marks of the U.S. 7th Fleet similarly spoke to Blitzer on Monday . `` We are looking over a -- now -- a very large search area in the Gulf of Thailand , and then yesterday , an area northwest of the Strait of Malacca . But as the hours go by , that area keeps getting bigger and bigger when you account for currents and the wind , '' he said , while aboard the USS Blue Ridge , which is assisting in the search . Marks continued : `` It 's a very large search area , but still a mystery -- still a lot of question marks . '' CNN 's Saeed Ahmed contributed to this report .
NEW : `` They will find it ... They have to , '' says CNN aviation correspondent . Malaysia Airlines Flight 370 disappeared three days ago . Nearly three dozen aircraft and 40 ships have so far failed to find any sign of the aircraft . The search area grows by the day , as `` crucial times '' passes , one expert says .