[6] Investigators believe that a bomb was put on the aircraft at Sharm El Sheikh, with the goal of causing airlines to suspend flights to that airport.

Lead investigator Ayman al-Muqaddam said that other possible causes of the crash included a fuel explosion, metal fatigue, and lithium batteries overheating.

[12] The Russian Federal Security Service announced on 17 November 2015 that they were sure that it was a terrorist attack, caused by an improvised bomb containing the equivalent of up to 1 kilogram (2.2 lb) of TNT that detonated during the flight.

[19] In March 2020, an Egyptian appeals court ruled the crash was not an act of terrorism, and it dismissed lawsuits against government officials, Metrojet, and Ingosstrakh.

[26][29] Flight 9268 left Sharm El Sheikh at 05:50 EGY (03:50 UTC) on 31 October 2015[2] for Pulkovo Airport in Saint Petersburg, Russia, with 217 passengers and seven crew members on board.

As the search area widened, the Egyptian team found the body of a child about 8 kilometres (5 mi; 4 nmi) from the wreckage, indicating that the aircraft had broken up in mid-air, confirmed by Russian investigator Viktor Sorochenko.

[31]: 4  On the same day, Egyptian Civil Aviation Minister Hossam Kamel said that air traffic control recordings did not show any distress calls, nor change of route requests by the pilots.

Egyptian Foreign Minister Sameh Shoukry promised to work closely with Russian officials and investigators to find the cause of the accident.

[56] On 4 November, Egypt's Civil Aviation Ministry Investigators reported that the cockpit voice recorder (CVR) was partially damaged and much work was required to extract data from it.

[58] An unnamed official quoted by Reuters said that Flight 9268's tail section separated from the main body of the fuselage and was burning, which could indicate an explosion.

[62] British aviation experts travelled to Egypt to assess airport security; the UK government Cobra emergency committee, chaired by the Prime Minister, considered their findings.

[64] Paul Adams, BBC world affairs correspondent, said that Prime Minister David Cameron's spokesperson left little doubt that the British government believed the aircraft was brought down by a bomb.

Lead investigator Ayman al-Muqaddam said that other causes, such as lithium batteries overheating, a fuel explosion, or metal fatigue in the structure, still needed to be definitively ruled out.

[12] On 17 November 2015, the Russian security service chief Alexander Bortnikov announced that their investigation had concluded that a "terror act" brought down Metrojet Flight 9268 after traces of explosives were found in the wreckage.

[72] Reuters reported that, according to security sources, two employees of Egypt's Sharm El Sheikh airport had been detained for questioning over the crash on suspicion of putting a bomb on board the flight.

[59] Natalya Trukhacheva, the ex-wife of co-pilot Sergei Trukhachev, said in an interview with NTV that her ex-husband had complained to their daughter about the aircraft's technical state.

The crash of Flight 123 was caused by an incorrect repair of the aircraft's tail section following the tailstrike, which left the rear pressure bulkhead of the airliner vulnerable to metal fatigue and ultimately resulted in explosive decompression.

[82] On 2 November, Metrojet spokesman Alexander Smirnov insisted that the aircraft was 100% airworthy and that its crew was "very experienced", showing certificates the airline had received in 2014, later adding that the tailstrike incident in Cairo had been fully repaired and the engines had been inspected on 26 October, five days before the crash.

[59] On 2 November, Metrojet spokesman Alexander Smirnov ruled out technical fault and pilot error as the cause of the crash and blamed an "external force".

[86] Russian Transport Minister Maksim Sokolov dismissed the claims as "fabrications" due to a lack of evidence from Egyptian civil aviation, from security officials and from air traffic data.

[88] On the same day, a source on the committee analysing the flight recorders said he believed that the aircraft was not struck from the outside and that the pilot did not make a distress signal before it disappeared from radar.

[88] All flights due to leave Sharm El Sheikh for Britain were delayed as a "precautionary measure" to allow experts to assess security.

[93] On the morning of 5 November Air France-KLM announced that it would not allow hold baggage on its flight out from Cairo that day; over half of the booked passengers refused to fly.

[106][107] The British government and head of Emirates Airlines stated that airport security throughout the Middle East could be significantly overhauled as a result of the bombing.

About 70 employees lost their clearance to work in secure zones of Paris's Orly and Charles de Gaulle airports due to suspected extremist links.

[117] On 17 November Russia's security chief said the cause of the attack was an act of terror, and the Russian Government offered a US$50 million reward for any information leading to the arrest of the perpetrators.

[119][needs update] During a trade visit to Cairo in April 2018, Ukrainian foreign minister Pavlo Klimkin discussed the bombing and its effects.

[122] At a joint press conference with Cameron, President Sisi said Egypt would co-operate on improved security measures at Sharm El Sheikh airport.

Since flights from other countries were continuing, the UK government reminded its citizens of its ongoing recommendation against all but essential travel by air to or from Sharm el Sheikh.

[127] On 6 November, the French satirical weekly magazine Charlie Hebdo published cartoons referring to the tragedy, one with pieces of an aircraft falling on an ISIL fighter with the caption: "Russia's air force intensifies its bombing."