The pilot of Metrojet flight 9268, an Airbus A321, radioed air traffic control to report technical difficulties shortly before it disappeared from radar screens some 23 minutes after take-off.
All 224 passengers on board have died after the plane crashed into the Sinai peninsula in Egypt.
The flight took off from the holiday resort of Sharm el-Sheikh at 5.58am local time. The flight was bound to the Russian city of St Petersburg.
It disappeared from radar screens at 6.20am.
It's now been reported that the pilot radioed air traffic control to report technical difficulties and planned an emergency landing at the nearest airport.
The plane vanished from radar screens while flying at an altitude of 31,0000 ft over the mountainous area of Arish.
An official from the Egyptian aviation authorities reported the pilot made the call - but this has been seemingly contradicted by Metrojet which said the plane was in full working order and operated by a very experienced crew.
Separately, Sky News are reporting that the wife of the co-pilot on board the flight has claimed her husband was "anxious" about the condition of the plane.
Sergei Truckahev reportedly called his daughter to say "the technical condition of the aircraft left much to be desired", his wife told Russian media.
He called his daughter shortly before it crashed into a mountainous are.
According to FlightRadar24, the aircraft slowed before beginning a rapid descent at 6,000ft per minute before it disappared.
“It was climbing quite normally when after 23 minutes when it passed 30,000ft it suddenly started to lose speed,” analyst Mikail Robertson told the BBC.
“It went down from 400 knots to 62 knots and then it suddenly started to drop very fast…after about 20 seconds we lost the signal from this aircraft.”
Investigators believe the plane crashed in a "vertical fashion", and the tail of the plane split.
Islamic State have claimed responsibility for the crash - however Eyptian authorities have dismissed this while the Russian government says such a statement "can't be considered accurate".
A statement published by Isis’ propaganda agency said: “The fighters of the Islamic State were able to down a Russian plane over Sinai province that was carrying over 220 Russian crusaders. They were all killed, thanks be to God.”
However, the statement did not say how the plane was supposedly taken down.
A video shared online by supporters of Islamic State claims to show the plane exploding before going down in a trail of smoke. However, many observers have said the video is a fake.
The plane was an Airbus A321-200 with registration number EI-ETJ. It is owned and registered to a company based in Ireland and was leased to Metrojet. Metrojet were responsible for all checks on the plane.
A spokesperson for Metrojet said it had been maintained according to international regulations and had undergone routine pre-flight checks..
More details surrounding the victims of the crash have begun to emerge.
All 224 people on board were Russian with the exception of three Ukranian nationals.
The youngest passenger is reported as being a 10-month-old baby. Reports also state that up to 25 children were on board. Some 138 passengers were female, while the remainder were male. Another two siblings aged two and three were also on the plane, as were another two children aged two and eleven. The remainder of the children were understood to be teenagers.
Most of the passengers were holiday makers, returning from the popular resort town of Sharm el-Sheikh.
The A321-200 is the largest member of the Airbus A320 family - and is used by more than 300 operators around the world.
Egyptian and Russian authorities have launched a joint investigation to establish what lead to the crash - Airbus have also launched an investigation. Wreckage from the site will be analysed in a bid to determine what led to the crash. Both black boxes have been recovered.
Recovery teams are working on the site today to remove the remains of all passengers. It's believed some 123 bodies were transported to the official morgue in Cairo yesterday evening.
Relatives in Russia are being offered free flights to Egypt and Metrojet say they are providing support and counselling.
Russian officials are questioning Metrojet officials, as well as staff belonging to the tour operator. They are also analysing fuel samples at the location where the jet refuelled in Samara.
President Vladimir Putin has declared today a day of mourning for Russia.