An earlier version of this story initially appeared on CNN.com in 2014.

(CNN) What happened to Malaysia Airlines Flight 370 before it dropped off radar?

Here's how experts and officials reconstructed key moments of the flight in the immediate aftermath of its disappearance with 239 people aboard.

12:41 a.m.

Takeoff

All tracking systems are working as the Boeing 777-200ER takes off from the Malaysian capital of Kuala Lumpur, headed for Beijing.

1:07 a.m.

ACARS sends communication

One of the plane's communication systems sends what turns out to be its last transmission, according to Malaysia Airlines CEO Ahmad Jauhari Yahya.

"It showed nothing unusual. The 1:07 a.m. transmission showed a normal routing all the way to Beijing," according to a statement from Malaysia's Ministry of Transport.

The Aircraft Communications Addressing and Reporting System is the onboard computer that collects information -- a lot of it -- about aircraft and pilot performance. It's akin to computers in automobiles that track oil levels and engine performance.

Aboard aircraft, ACARS computers measure thousands of data points and send the information via satellite to the airline, the engine manufacturer and other authorized parties, according to CNN aviation and airline correspondent Richard Quest.

The information is useful for operations, maintenance, scheduling and performance purposes, Quest said.

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1:19 a.m.

Voice check-in

MH370 First Officer Fariq Abdul Hamid, left, and Captain Zaharie Ahmad Shah.

Someone in the cockpit makes a voice check-in with air traffic controllers as the plane is apparently leaving Malaysian airspace and entering Vietnamese airspace. Initial investigations indicate it was the co-pilot, Fariq Abdul Hamid, according to Malaysia Airlines officials.

"All right, good night" were the final words from the cockpit, said Zulazri Mohd Ahnuar, a Malaysian civil aviation officer.

The phrase "good night" is the radio parlance used by pilots when executing a handover from one airspace to another, Quest said.

"That is normal. That happens a gazillion times," Quest said. "'All right, good night' is a pleasantry at the end of radio communication."

1:21 a.m.

Transponder off

The plane's transponder stops communicating at 1:21 a.m., said Azharuddin Abdul Rahman, director of the Malaysian Department of Civil Aviation.

A transponder sends electronic messages from the plane: "squawks" to radar systems about the flight number, altitude, speed and heading.

This is enormously useful information to air traffic controllers who are looking at scores of blips on their screens, and each blip is a plane emitting identifying information, thanks to the transponder.

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

With the transponder off, "now the plane is flying blind from the ground's point of view," Quest said. "If there is radar there, the radar will see a blip, but they won't know who it is, where they are going. They will just now know it's there."

That's because the transponder isn't sending identifying information about the plane. Shutting off the transponder is a simple turn of a switch in the cockpit, Quest said.

"The air traffic controller should notice. I suppose it would cause alarm. ... (The information from) a plane that you're monitoring all of a sudden disappears," Quest said.

1:22 a.m.

Plane disappears from Thai military radar

Thai military radar is tracking the plane's signal, but it disappears at 1:22 a.m., a Royal Thai Air Force spokesman told CNN.

1:28 a.m.

Thai radar picks up unknown aircraft

The Thai radar station in southern Surathani province picks up an unknown aircraft flying in a direction opposite to what Flight 370 had been traveling, a Royal Thai Air Force spokesman told CNN.

1:21 a.m. - 1:28 a.m.

Plane appears to change course

The plane appears to have changed course in this time frame. The Malaysian government has not said when or if the plane was reprogrammed to fly off course.

Again, according to the Malaysians, the last data from the ACARS at 1:07 a.m. indicated that it "showed normal routing all the way to Beijing."

About 1:30 a.m.

Civilian radar loses contact with plane

Malaysian air traffic controllers in Subang, outside Kuala Lumpur, lose contact with the plane over the Gulf of Thailand between Malaysia and Vietnam at coordinates 06 55 15 N and 103 34 43 E.

1:37 a.m.

Expected ACARS transmission doesn't happen

The ACARS was supposed to transmit a half-hour after it last did so. Therefore, it was supposed to transmit at 1:37 a.m. -- but it didn't, Yahya said.

So, the ACARS stopped communicating sometime between 1:07 and 1:37 a.m.

It's a significant event: Turning off ACARS takes know-how, Quest said.

If the flight were hijacked or a target of terrorism, cutting off ACARS would be a strategic move because the system reports to satellites anything being done to the aircraft, Quest said.

2:15 a.m.

Military radar detection

Though the Malaysian plane is not transmitting information -- by ACARS or transponder -- radar on the ground or elsewhere can still detect a plane in the air.

According to a Malaysian Air Force official, military radar tracked the plane as it passed over the small island of Pulau Perak in the Strait of Malacca.

At this point, the plane was hundreds of miles off course. In fact, it was on the other side of the Malay Peninsula.

Military radar showed that it flew in a westerly direction back over the Malay Peninsula, Malaysian Prime Minister Najib Razak said. This was the last time any civilian or military radar is known to have tracked the aircraft.

The focus now then turned to searching for the missing flight in the southern Indian Ocean. "The southern scenario seems more plausible," a US official said.

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The Malaysian military handed over its raw radar data to US and British officials, apparently setting aside concerns about any sensitive military intelligence.

Quest called this sharing of information a "huge" development in the case.

"They don't want anyone to know how good their radar is. They obviously decided that doesn't matter," he said.

"We don't know much about the Malaysian military and that has been one of the issues," Quest added. "It appears that Malaysia was providing an interpretation of the analysis -- and not the raw data. Now they are handing over the raw data."

2:40 a.m.

Malaysia Airlines says it learns plane missing from radar

Malaysian air traffic controllers told Malaysia Airlines at 2:40 a.m. that Flight 370 was missing from radar, according to the airline.

2:40 - 3:45 a.m.

Malaysia Airlines preliminary search

During this time, the airline "sourced every communication possible to (Flight 370) to locate its whereabouts before declaring that it had lost contact with the aircraft," the company told CNN.

"During this period of uncertainty, Malaysia Airlines needed to establish facts by contacting other air traffic controllers and aircraft flying within the same route," the company said.

3:45 a.m.

Malaysia Airlines issues alert

Malaysia Airlines said it issued a "code red" alert that the plane was missing from radar.

The airline said "code red" is when it declares that a crisis requires immediate deployment of emergency response plans. It said it took about an hour to issue the alert because it was trying to locate the plane and confirm that it was missing. To verify, it used various measures, including sending messages to the plane and awaiting a response.

6:30 a.m.

Plane should have arrived in Beijing

This was the time that Malaysia Airlines Flight 370 should have landed in China's capital.

7:24 a.m.

Public announcement of disappearance

Malaysia Airlines announces the plane's disappearance on Facebook.

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8:11 a.m.

Satellite 'handshakes'

Najib revealed that a satellite tracked the plane at 8:11 a.m., more than seven hours after takeoff.

Najib didn't provide details on the satellite tracking, but it appears that orbiters high above the ocean detected the plane as the satellite or satellites attempted a series of "handshakes" -- or electronic connections -- with the plane below, Quest said.

It's likely that the plane didn't complete the handshake because its communication systems were disabled, Quest said.

Nevertheless, the satellites would have been able to trace a plane flying below them and would have extended an electronic message equivalent to a hailing: "There's a plane: Hello, hello, hello? Do you have anything for us?" Quest said.

The Malaysian Prime Minister said the "raw satellite data" confirms the plane was Flight 370. The US National Transportation Safety Board and the Federal Aviation Administration, along with Britain's Air Accidents Investigation Branch, concur, Najib said.

Photos: Remembering the passengers of MH370 There is still no way to know for sure why Flight MH370 ended, but we are learning more about the lives of those on board. CNN is remembering them through snapshots shared with us. Hide Caption 1 of 12 Photos: Remembering the passengers of MH370 Rodney and Mary Burrows were looking forward to becoming first-time grandparents after their return home to Australia. Hide Caption 2 of 12 Photos: Remembering the passengers of MH370 Australians Catherine and Robert Lawton were traveling with friends on vacation when the flight disappeared. Hide Caption 3 of 12 Photos: Remembering the passengers of MH370 Paul Weeks was traveling to Mongolia for a new job as an engineer. His wife says Paul left behind his watch and his wedding ring before the trip, in case anything happened to him while he was away. Anderson spoke with Paul's brother & sister who said they are coping by spending time together as a family. Hide Caption 4 of 12 Photos: Remembering the passengers of MH370 Chandrika Sharma, left, was on Flight 370; her daughter Meghna and husband K.S. Narendran wait patiently, trying to manage their anxiety and longing for her return. Hide Caption 5 of 12 Photos: Remembering the passengers of MH370 Muktesh Mukherjee and Xiaomo Bai had been vacationing in Vietnam and were on their way home to their two young sons in Beijing. Hide Caption 6 of 12 Photos: Remembering the passengers of MH370 76-year-old Liu Rusheng, an accomplished calligrapher and one of the oldest passengers on the flight, was in Malaysia to attend an art exhibition with his wife. Hide Caption 7 of 12 Photos: Remembering the passengers of MH370 Teens Hadrien Wattrelos and Zhao Yan are shown in a photo on Wattrelos' Facebook page. The photo is captioned, simply, "I love you," in French. Hide Caption 8 of 12 Photos: Remembering the passengers of MH370 Firman Chandra Siregar, 24, studied electrical engineering in Indonesia and was on his way to Beijing on board Flight 370 to start a new job at an oil company. Hide Caption 9 of 12 Photos: Remembering the passengers of MH370 Patrick Francis Gomes, center, was the in-flight supervisor for the missing plane. His daughter describes him as a quiet person with a sense of humor. Hide Caption 10 of 12 Photos: Remembering the passengers of MH370 Ch'ng Mei Ling, a Malaysian citizen who lives in Pennsylvania, is a process engineer at a chemical company. Hide Caption 11 of 12 Photos: Remembering the passengers of MH370 We do not have photos of all 239 passengers, but we wanted to remember that there are loved ones around the world missing them right now. View CNN's complete coverage of Flight 370. Hide Caption 12 of 12

"Due to the type of satellite data, we are unable to confirm the precise location of the plane when it last made contact with the satellite," Najib said.