Story highlights Grief counselor: Families are trying "to hold onto any little bit of hope"

Experts are divided over whether plane could have slipped past radar

Analyst: Radar blind spots could be determined "easily"

USS Kidd pulls out of the search for the missing plane

Could a massive passenger jet slip past radar, cross international borders and land undetected?

That's a key question investigators are weighing as they continue the search for Malaysia Airlines Flight 370, which vanished March 8 on a flight between Kuala Lumpur, Malaysia, and Beijing.

Radar does have some blind spots, and it's possible to fly at lower altitudes to avoid being spotted, analysts told CNN.

But experts are divided over whether that could be what happened to the missing Boeing 777.

Jeffrey Beatty, a security consultant and former FBI special agent, says someone could have planned a route that avoided radar detection.

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Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 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 on March 8, 2014. 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, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 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, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43

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"It certainly is possible to fly through the mountains in that part of the world and not be visible on radar. Also, an experienced pilot, anyone who wanted to go in that direction, could certainly plot out all the known radar locations, and you can easily determine, where are the radar blind spots?" he said. "It's the type of things the Americans did when they went into Pakistan to go after Osama bin Laden."

On Monday, the Malaysian newspaper New Straits Times reported that the plane may have flown low to the ground -- 5,000 feet or less -- and used mountainous terrain as cover to evade radar detection. The newspaper cited unnamed sources for its reporting, which CNN could not immediately confirm.

And a senior Indian military official told CNN on Monday that military radar near the Andaman and Nicobar Islands isn't as closely watched as other radar systems. That leaves open the possibility that Indian radar systems may not have picked up the airplane at the time of its last known Malaysian radar contact, near the tiny island of Palau Perak in the Strait of Malacca.

U.S. officials have said they don't think it's likely the plane flew north over land as it veered off course. If it had, they've said, radar somewhere would have detected it. Landing the plane somewhere also seems unlikely, since that would require a large runway, refueling capability and the ability to fix the plane, the officials have said.

Malaysian officials said Monday that they were not aware of the Malaysian newspaper's report.

"It does not come from us," said Malaysia Airlines CEO Ahmad Jauhari Yahya.

Analysts interviewed by CNN said that it would be extremely difficult to fly such a large aircraft so close to the ground over a long period of time, and that it's not even clear that doing so would keep the plane off radar scopes.

"Five-thousand isn't really low enough to evade the radar, and that's kind of where general aviation flies all the time anyway, and we're visible to radar," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation.

"It just seems really highly improbable, unless we've been overestimating a lot of other countries' radar system capabilities," said Daniel Rose, an aviation and maritime attorney.

Buck Sexton, a former CIA officer who's now national security editor for TheBlaze.com, said radar would have detected the plane if it flew over land.

"This is a bus in the sky. It's a lot harder to get under the radar with this kind of thing than I think most people realize," he said. "So really, while the search I know has extended to this vast area stretching up into (the nations and central or south Asia), clearly there really should be much more of a search over open water, because this is not getting past people's radars."

It wouldn't be easy to avoid radar detection, experts say, but it could be done.

"Anything like this is possible," radar expert Greg Charvat told CNN's Piers Morgan Live . "But to do it, you'd have to have very detailed information of the type of radars, their disposition, their heights and their waveforms to pull that off."

Different countries would likely be using different radar systems, he said, but it's unclear how advanced the technology is in many countries.

"It took a great deal of skill to do this," CNN aviation analyst Jim Tilmon said. "I think somebody was at the controls who understood the value of altitude control to eliminate the possibility of being spotted and tracked on radar."

Whoever was in control in the cockpit, he said, "really had the ability to map out a route that was given the very best chance of not being detected."

One other possibility, he said: the plane could have shadowed another plane so closely that it slipped by radar detection.

Other analysts say that would require so much skill that it would be nearly impossible to pull off without getting caught.

There's another possible wrinkle, experts say. Some countries may be hesitant to reveal what they've seen on radar.

"They want to protect their own capabilities," Beatty said. "Their intelligence services are not going to want to publicize exactly what their capabilities are."

Here are other developments in the search and investigation, as search crews from 26 nations continue scouring vast swaths of ocean and land for any trace of the airliner:

Timeline clarification

Ahmad Jauhari said Monday that it wasn't clear whether the final words from the cockpit came before or after the plane's data-reporting system was shut down. Earlier, Malaysian authorities had said the message "All right, good night" came after the system had been disabled.

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The voice message came from the plane's copilot at 1:19 a.m. Saturday, March 8, Ahmad Jauhari said. The data system sent its last transmission at 1:07 a.m. and was shut down sometime between then and 1:37 a.m. that day, Ahmad Jauhari said.

Grief counselor: Families holding on to hope

As authorities keep searching for the plane, the loved ones of the 239 passengers and crew members who were on board are left in limbo.

Helping them has been difficult, grief counselor Paul Yin told CNN's "AC360."

"Grief counseling, or any kind of recovery from this, has to have a starting point. And the starting point is having a verdict of what happened," he said. "Without a starting point, every day people's emotions go up and down, from hope to despair."

He heard some family members cheer when they learned that hijacking was possibly what caused the plane's disappearance.

"Because that means they could still be alive," he said. "They're trying to hold onto any little bit of hope."

Chinese response

China said Monday that it had deployed 10 ships, 21 satellites and multiple aircraft to aid in the search.

Premier Li Keqiang spoke with Malaysian Prime Minister Najib Razak to ask for more information to help speed the search along, according to a statement posted on the Chinese government website.

A top Malaysian official denied the allegation that his country had held back information about the missing flight.

"Our priority has always been to find the aircraft. We would not withhold any information that could help," Acting Transport Minister Datuk Seri Haishammuddin Tun Hussein told reporters. "But we also have a responsibility not to release information until it has been verified by the international investigations team."

U.S. Navy pulls out destroyer

The USS Kidd and its helicopters have stopped combing the Andaman Sea and are no longer part of search efforts for the missing plane, the Navy said.

The move is partially because Australians are taking over the majority of the searching in that area, U.S. officials said. A U.S. P-8 aircraft will move to Perth, Australia, to be based there for searching.

Fewer U.S. assets will be involved in the search for the missing plane, but U.S. officials said the P-8 will be able to cover a wider range of ocean more quickly than the ship could.

"This is actually much more effective for the overall search," Cmdr. William Marks of the U.S. 7th Fleet told CNN's Wolf Blitzer Monday.

"The real challenge is this huge expanse of water. I keep saying, if you superimposed a map of the U.S. on here, it'd be like trying to find someone anywhere between New York and California. so that's the challenge here," he said. "We have amazing, dedicated air crews. it's just a matter of how much area we can search."