(CNN) — A wide search. And a ticking clock.
The box containing the flight-data and cockpit-voice recorders of missing Malaysia Airlines Flight 370 has batteries designed to keep it sending out pings for 30 days.
The search is now in its 12th day, covering a total area roughly the size of the continental United States. That leaves 18 days until the batteries are expected to run out.
Investigators hope the recorders may reveal vital information about why the passenger jet carrying 239 people veered dramatically off course and disappeared from radar screens. But they have to find them first.
Searchers from at least 26 countries have a formidable task in pinpointing the plane’s location somewhere along two vast arcs, one stretching deep into the Asian landmass, the other far out into the Indian Ocean.
A relative of Chinese passengers aboard the missing Malaysia Airlines jet waits for a news briefing by officials in Beijing on Tuesday, March 18. The Boeing 777 disappeared during a March 8 flight from Kuala Lumpur, Malaysia, to Beijing.
A relative of a Chinese passenger aboard Malaysia Airlines Flight 370 tells reporters in Beijing on March 18 about a hunger strike to protest authorities’ handling of information about the missing jet.
A member of Indonesia’s National Search and Rescue Agency joins in a search for the missing plane in the Andaman
Sea area around the northern tip of Indonesia’s Sumatra on Monday, March 17.
Relatives of passengers aboard Malaysia Airlines Flight 370 watch a news program about the missing plane as they await information at a hotel ballroom in Beijing on March 17.
Malaysian Transportation Minister Hishamuddin Hussein, center, shows maps of the search area March 17 at a hotel in Sepang, Malaysia, next to the Kuala Lumpur International Airport.
U.S. Navy crew members assist in search-and-rescue operations Sunday, March 16, in the Indian Ocean.
Indonesian personnel watch over high seas during a search operation in the Andaman Sea on Saturday, March 15.
A foam plane, which has personalized messages for the missing flight’s passengers, is seen at a viewing gallery March 15 at Kuala Lumpur International Airport.
A member of the Malaysian navy makes a call as his ship approaches a Chinese Coast Guard ship in the South China Sea on March 15.
A Indonesian ship heads to the Andaman Sea during a search operation near the tip of Sumatra, Indonesia, on March 15.
Elementary school students pray for the missing passengers during class in Medan, Indonesia, on March 15.
Col. Vu Duc Long of the Vietnam air force fields reporters’ questions at an air base in Ho Chi Minh City, Vietnam, after a search operation on Friday, March 14.
Members of the Chinese navy continue search operations on Thursday, March 13. The search area for Flight 370 has grown wider. After starting in the sea between Malaysia and Vietnam, the plane’s last confirmed location, efforts are expanding west into the Indian Ocean.
A Vietnamese military official looks out an aircraft window during search operations March 13.
Malaysian air force members look for debris on March 13 near Kuala Lumpur.
A relative of a missing passenger watches TV at a Beijing hotel as she waits for the latest news March 13.
A member of the Indonesian National Search and Rescue Agency scans the horizon in the Strait of Malacca on Wednesday, March 12.
Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12.
Journalists raise their hands to ask questions during a news conference in Sepang on March 12.
Indonesian air force officers in Medan, Indonesia, examine a map of the Strait of Malacca on March 12.
A member of the Vietnamese air force checks a map while searching for the missing plane on Tuesday, March 11.
Iranians Pouri Nourmohammadi, second left, and Delavar Seyed Mohammad Reza, far right, were identified by Interpol as the two men who used stolen passports to board the flight. But there’s no evidence to suggest either was connected to any terrorist organizations, according to Malaysian investigators. Malaysian police believe Nourmohammadi was trying to emigrate to Germany using the stolen Austrian passport.
An Indonesian navy crew member scans an area of the South China Sea bordering Indonesia, Malaysia and Thailand on Monday, March 10.
Vietnam air force Col. Le Huu Hanh is reflected on the navigation control panel of a plane that is part of the search operation over the South China Sea on March 10.
Relatives of the missing flight’s passengers wait in a Beijing hotel room on March 10.
A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews before returning to search for the missing plane Sunday, March 9, in the Gulf of Thailand.
Members of the Fo Guang Shan rescue team offer a special prayer March 9 at Kuala Lumpur International Airport.
A handout picture provided by the Malaysian Maritime Enforcement Agency shows personnel checking a radar screen during search-and-rescue operations March 9.
Italian tourist Luigi Maraldi, who reported his passport stolen in August, shows his current passport during a news conference at a police station in Phuket island, Thailand, on March 9. Two passengers on the missing Malaysia Airlines flight were reportedly traveling on stolen passports belonging to Maraldi and an Austrian citizen whose papers were stolen two years ago.
Hugh Dunleavy, commercial director of Malaysia Airlines, speaks to journalists March 9 at a Beijing hotel where relatives and friends of the missing flight’s passengers are staying.
Vietnamese air force crew stand in front of a plane at Tan Son Nhat airport in Ho Chi Minh City on March 9 before heading out to the area between Vietnam and Malaysia where the airliner vanished.
Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9.
The Chinese navy warship Jinggangshan prepares to leave Zhanjiang Port early on March 9 to assist in search-and-rescue operations for the missing Malaysia Airlines flight. The Jinggangshan, an amphibious landing ship, is loaded with lifesaving equipment, underwater detection devices and supplies of oil, water and food.
Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China’s Hainan province on March 9. The vessel is carrying 12 divers and will rendezvous with another rescue vessel on its way to the area where contact was lost with Malaysia Airlines Flight 370.
The rescue vessel sets out from Sanya in the South China Sea.
A family member of missing passengers is mobbed by journalists at Kuala Lumpur International Airport on Saturday, March 8.
A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported March 8. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia’s state news agency, Bernama, reported on March 10.
Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8.
Malaysia Airlines official Joshua Law Kok Hwa, center, speaks to reporters in Beijing on March 8.
A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8.
Wang Yue, director of marketing of Malaysia Airlines in China, reads a company statement during a news conference at the Metro Park Lido Hotel in Beijing on March 8.
Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8.
A woman asks a staff member at the Beijing airport for more information on the missing flight.
A Malaysian man who says he has relatives on board the missing plane talks to journalists at the Beijing airport on March 8.
Passengers walk past a Malaysia Airlines sign on March 8 at Kuala Lumpur International Airport.
Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference on March 8 at a hotel in Sepang. “We deeply regret that we have lost all contacts” with the jet, he said.
Photos: The search for Malaysia Airlines Flight 370
See new video of Flight 370 pilot
Watch Flight Simulator Attempt Theory
Was turn pre-programmed in computer?
Tracking Malaysia Air flight 370
“The odds of finding the pinger are very slim,” said Rob McCallum, an ocean search specialist. “Even when you know roughly where the target is, it can be very tricky to find the pinger. They have a very limited range.”
A U.S. government source familiar with the investigation told CNN that based on present search patterns and available data, he believes it’s far more likely that the plane would be located in the southern arc of the search area.
“This is an area out of normal shipping lanes, out of any commercial flight patterns, with few fishing boats and there are no islands,” he said, warning that the search could well last “weeks and not days.”
Technology put to use
Some of the nations involved in the hunt are deploying an impressive array of technology, including satellites and high-tech submarine-hunting planes, as they try to narrow the search area.
They’re also trawling through existing radar and satellite data for clues.
Australia said Wednesday that the area of the southern Indian Ocean where it is searching for the plane has been “significantly refined.”
The new area is based on work done by the U.S. National Transportation Safety Board on “the fuel reserves of the aircraft and how far it could have flown,” said John Young of the Australian Maritime Safety Authority.
But Australian ships and aircraft have so far seen nothing connected to the missing plane, Australian authorities said.
Small details emerge
Much of what has emerged in recent days has filled in a few more details about the early part of the missing Boeing 777-200′s flight.
But clear information on what went on in the cockpit and where exactly the errant jet went after it vanished from Malaysian military radar remains frustratingly elusive.
On Tuesday, for example, a law enforcement official told CNN that the aircraft’s first major change of course was almost certainly programmed by somebody in the cockpit. The change was entered into the plane’s system at least 12 minutes before a person in the cockpit, believed to be the co-pilot, signed off to air traffic controllers.
But that disclosure only left more questions about the reason behind the reprogrammed flight path.
Some experts said the change in direction could have been part of an alternate flight plan programmed in advance in case of emergency; others suggested it could show something more nefarious was afoot.
The Thai military, meanwhile, said it had spotted the plane turning west toward the Strait of Malacca early on March 8. That supports the analysis of Malaysian military radar that has the plane flying out over the Strait of Malacca and into the Indian Ocean.
But it didn’t make it any clearer where the plane went next. Authorities say information from satellites suggests the plane kept flying for about six hours after it was last detected by Malaysian military radar.
Who was at the controls?
Malaysian authorities, who are coordinating the search, say the available evidence suggests the missing plane flew off course in a deliberate act by someone who knew what they were doing.
Figuring out who that might be has so far left investigators stumped.
Particular attention has focused on the pilot and first officer on Flight 370, but authorities are yet to come up with any evidence explaining why either of them would have taken the jetliner off course.
And some experts have warned against hastily jumping to conclusions about the role of the pilots.
“I’ve worked on many cases were the pilots were suspect, and it turned out to be a mechanical and horrible problem,” said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation. “And I have a saying myself: Sometimes an erratic flight path is heroism, not terrorism
China says it has found nothing suspicious during background checks on its citizens on the flight — a large majority of the plane’s passengers.
Searchers face deep ocean
Malaysian Transport Minister Hishammuddin Hussein, the country’s public face of the search efforts, has repeatedly said at news conferences that little is likely to be established about the mysterious flight until the plane is found.
But in the Indian Ocean, where Australia and Indonesia have taken the lead in the hunt, some of the depths searchers are dealing with are significant.
The Bay of Bengal, for example, which lies between Myanmar and India, has depths of between about 4,000 and 7,000 meters (13,000 feet and 23,000 feet), according to McCallum.
Wreckage and bodies of passengers from Air France Flight 447, which crashed into the Atlantic Ocean in 2009, were found at depths of around 12,000 feet by unmanned submarines.
It took four searches over the course of nearly two years to locate the bulk of the wreckage and the majority of the bodies of the 228 people on board Flight 447. It took even longer to establish the cause of the disaster.
Right now, authorities don’t even know for sure if the missing Malaysian plane crashed or landed — or where.
CNN has talked to more than half a dozen U.S. military and intelligence officials who emphasize that while no one knows what happened to the plane, it is more logical to conclude it crashed into the Indian Ocean.
The officials say there is no evidence that any U.S. satellite data registered an unknown aircraft in any of the Asian countries along the path the plane may have taken. According to these officials, it is overwhelmingly likely if the plane had crashed on land, there would be some evidence of that, and if it had landed, someone would have seen it.
Politician: Pilot supported me but was no hijacker
Could Malaysia Airlines Flight 370 have slipped by radar?
Malaysia Airlines passenger’s partner says she’s certain her soulmate is alive
Key moments emerge in tracking plane
CNN’s David Fitzpatrick, Kyung Lah, Evan Perez, Mariano Castillo and Catherine E. Shoichet contributed to this report.