Story highlights Could the plane be intact and in the hands of hijackers?

Is there a possibility that it caught fire?

What about the absence of cell phone contact?

The mystery of Malaysia Airlines Flight 370 raises countless questions. CNN analysts, contributors and correspondents have been searching for answers.

Here are some of the viewer questions posted to Twitter with the hashtag #370Qs and addressed by a panel assembled by CNN's Don Lemon.

@markydcote asked, "The Himalayas are vast. Is it possible the plane could have crashed there where radar coverage may be spotty?"

CNN correspondent Martin Savidge checked out that possible path in a flight simulator: "Well, essentially here's the scenario we set up. These are the Himalayan Mountains, and what we're trying to do is simulate flying through them. Apparently trying to do it below radar. In other words, using the mountain as kind of cover. The 777 was never designed to be a fighter aircraft, and even though we're in a simulator and even though I know that none of this is real, I've got to say that the way that the whole horizon keeps banking and yanking here is really uncomfortable. The aircraft is doing over 230 knots, as we find our way through the steep, narrow mountain passes here. You can hear all the alarms going off warning that we're way too low, and even though we're 1600 feet in the air, we're actually only 320 feet off the deck." "It is a simulation, but if somebody was trying to do this at night, there's no way. You would end up on one of these mountainsides here. So, it's impressive to watch, but really, this is just fantasy here. There's no way an aircraft like this would fly this low in the Himalayan Mountains."

@sharma_thakur99 asked, "Is there a possibility that it caught fire and radar, etc., wasn't manually shut off but an accident?"

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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

CNN Reporter Stephanie Elam spoke with former Trans World Airlines captain Barry Schiff about this: "You know, what we're given here is a large jigsaw puzzle that has 1,000 pieces and someone tossed 20 pieces at us and said, "Here figure out what this is supposed to represent,'" Schiff said, who flew jet liners for 34 years. His theory about what happened on flight 370? A problem on board. "If you have a serious problem aboard a jetliner like a fire, one thing you're going to want to do is get on the ground as soon as possible. And turning back towards Malaysia, towards a large airport is the first thing I would do. The most imperative thing is to take care of that fire. The last thing you're going to do is communicate unless you have the time to do it because no one on the ground can help you." He doesn't believe the idea that the pilots tried a water landing. "I seriously doubt that anyone would try to land a jetliner in the water at night. Imagine hitting the water at 100, 200, 300 miles an hour. It's going to make the airplane splatter into pieces."

@fstaylor asked, "Anyone been able to investigate the men traveling on the passports yet, any connection to the pilots?"

Jeff Beatty, national security expert: "I think that really leads to the question of: 'Were there people that were helping the pilots.'" "Obviously, there was no duress signal given from the pilots to the people they were communicating with." "There is a way to communicate duress not only with the transponder codes but also what you say verbally. So, if, in fact...(had they) been coerced and unwillingly turned the airplane, they could have given a verbal distress indicator... They didn't do that." "Perhaps they did have other people on the airplane with them; they willfully made this course deviation, and when we look at, well, who's suspicious? The mere act of taking and traveling with false passports certainly makes those people suspicious."

@742carol asked, "Often thieves get away with big heists. 777 would (be) worth money in the black market."

Science writer Jeff Wise: "There's a secondary market. You can go online and find them listed, and they are not worth a gigantic amount of money. It's like $50 million for a secondhand 777. Bear in mind that is not one that is hot. You've got to file off the serial numbers and so forth. So there's probably easier ways to get your hands on a few million bucks."

@michaelbuis asked, "What intelligence value (is there) to the employees of Semiconductor China Telecom and business machines ZTE and Huawei (being on the plane)?"

Arthur Rosenberg, aviation lawyer, aviation engineer and pilot: "It's my understanding those employees actually had a background in sophisticated radar, and there may have actually been at least one of those employees who had some piloting experience. So, the fact that they were actually on this plane, I think, is significant." "I have to say, at 1:07, when the ACARS system reported that there was a program change for the heading in the airplane, followed by 12 minutes later when the pilot made his infamous remark 'all right, good night'... pilots don't make their change in course mid-flight without getting permission from air traffic control. They had 12 minutes to talk to air traffic control...and did not do that. I think that this -- this was a well-laid plan."

@tristanrachman asked, "Why would one program a computer system if they didn't plan on landing somewhere?"

Mary Schiavo: "Ordinarily, you program your flight computers for places you don't intend to land, because you have to have secondary airports, and you have to have emergency plans before you ever take off. You have to have enough fuel to get to your primary and secondary (destinations) in case something happens. So, you actually...program and have flight coordinates for airports other than the ones that you're going to, but it's to deal with emergencies or weather or problems at the airport." "So, it's just a backup plan."

@bibisir asked, "Could pilot depressurize plane to cause passengers to pass out?"

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CNN aviation analyst and retired commercial pilot Jim Tilmon: "Yes, it can deprive the cabin of oxygen. And they don't have to do it for a very long time because you just cannot survive -- just a matter of minutes -- without oxygen. You go into kind of a hypoxia sleep, and you just don't wake up. And the crew has, of course, oxygen masks. They have a different source of oxygen that they can use, and they can put that mask on. It's a full face mask, and they can indeed breathe 100% oxygen for a while. It's far-fetched. It's awful to think of, but it is possible ... The masks would drop automatically. They do when you go through a certain altitude in the cabin. They automatically drop. The thing is that you have a tiny canister in each one of those overhead bins, and they are your oxygen generators. They only run for a relatively short length of time. That's why the protocol is if you do have an oxygen problem, you immediately go into a descent to get down into breathable oxygen, so that your passengers are going to be all right. And that's a pretty good drop -- that's a controlled dive, you might say, to about 14,000 feet."

@HerbOkam asked, "Is there any possibility of the airplane being completely intact at the bottom of the ocean hence the reason for no floating debris?"

Science writer Jeff Wise: "If it was in one piece, that would imply that the pilot had come in and done a gentle sort of Sullenberger kind of landing like he did on the Hudson where everything is in one piece. The problem with that is that you get the life rafts, deploying the life rafts, which are equipped with emergency locator beacons. In a way, It's either that or you do a high speed sort of supersonic descent where the thing just breaks into a million pieces. And if your goal is to leave no trace, then you'd be better off like that. That leaves millions of tiny pieces floating around. It's hard to imagine a scenario in which you ditch or crash in the ocean and there isn't some trace left."

@Bevie246 asked, "Are the authorities looking at the possible scenarios should the plane be intact and in the hands of hijackers?"

Former Inspector General of the U.S. Department of Transportation Mary Schiavo: "I certainly hope that they're looking at that, because there were so many lessons in the investigations after September 11. But one that was clear in the investigation following September 11 and that was the plot, the hints, the clues, it was imagined and imaginable. We had a lot of intelligence, and as soon as it happened, evidence starting pouring in. I got two key pieces of evidence in plain brown envelopes delivered to my office anonymously. Just everyone wanted to help. And here we don't have that, which is disconcerting, so the authorities, governments around the world really have to dig deep because there doesn't seem to be any information forthcoming. I've called it an eerie silence right now."

@AdSecurity asked, "Is it possible someone 'stole' the plane to use if later on in a terror attack and they wanted us all to believe that it crashed in the ocean?"

Jim Tilmon: "Yes, that's possible, but there's so many possibilities that we just have to put this on a long list."

Former CIA counter-terrorism officer Jeff Beatty: "That certainly is one of the possibilities. There's about three other scenarios that I'd like to just highlight. One of them could be a high-value cargo. The aircraft might have been taken for a high-value cargo. Now that cargo could possibly be people, high-value people that are on board, or that cargo could possibly be something of great value in the hold. The second one is in the past, we've actually had aircraft become the venue for murder ... and finally, there's always ransom."

@Lavender4CC asked, "What have we been told about the absence of #MH370 cell phone contact? No photos, texts, calls ... That's incredible!"

Mary Schiavo: "The first question is why not the calls from the plane or calls to and from the plane and that's because this plane was not equipped with the most modern equipment to have on board wifi and cell phone service, so that means that these cell phones would have to rely upon going near a tower. Now, the plane did pass back over Malaysia, and that was a possibility but it would have had to hit a tower just like anyone else driving around on the ground or being lucky to get a tower. And then, actually, some phone company officials have said that the cell phone ringing was not indicative that the phone was still working, but merely that it was simply ringing through to the area or the switching station to go ahead and meet the cell phone. It didn't mean the cell phone itself was working."