New clues have emerged from the wreckage of Metrojet Flight 9268, prompting more speculation about whether there was a midair explosion and whether repair work from a previous accident may have played a role in the plane's demise.
The aircraft, headed from the Egyptian resort of Sharm el-Sheikh to St. Petersburg, Russia, crashed in the Sinai Peninsula on Saturday, killing all 224 people on board.
The plane's tail was found about 5 km (3 miles) away from the rest of the plane wreckage, the Russian state broadcaster Russia 24 reported. The outlet also said the rest of the wreckage did not show any signs of burning from a fire.
The distance from the tail to the rest of the debris could be telling — especially since the tail was previously damaged, CNN aviation analyst Mary Schiavo said.
"To me, it says (the tail) exited the plane before the explosive event and before the fire engulfed the plane," she said.
The same plane's tail struck a runway while landing in Cairo in 2001 and required repair, according to the Aviation Safety Network, which tracks aircraft incidents. At the time, the aircraft was registered to the Lebanese carrier Middle East Airlines, registration records show.
Schiavo, a former inspector general for the US Department of Transportation, said something could have gone wrong with the repair work after the tail strike. She said she once worked on a crash where a tail strike that had not been repaired well brought down a plane almost two decades later.
"A bad repair is like a ticking time bomb, because once it's on the plane, it stays with the plane forever," she said.
Airline company spokesman Andrei Averyanov said the plane had been damaged in 2001, but had most recently been thoroughly checked for cracks in 2013. Not enough time had passed for major cracks to develop to a critical size since then, he said.
The A321-200 was built in 1997. The aircraft had clocked around 56,000 flight hours over the course of nearly 21,000 flights, the plane maker said.
Officials have said all its inspections were in order.
The possibility of an explosion
Forensic experts trying to identify the 224 victims from the crash have divided the types of trauma into two categories: injuries from the fall, and injuries that align with an explosion — such as metal pieces in bodies, the St. Petersburg news outlet Fontanka reported.
But the experts said it's too early to say what actually caused the plane to crash.
Russia's state-run TASS news agency reported that Russian and Egyptian experts had not found any blast-related trauma during their preliminary examination of the bodies, citing a Russian source within the investigation.
Most of the bodies retrieved at the crash site are intact, a medical source in Sinai told CNN.
That doesn't eliminate the possibility that an explosion occurred, said CNN safety analyst David Soucie, a former accident investigator for the Federal Aviation Administration.
"A blast would not have to be very large … to rupture the hull of that aircraft," he said.
On Wednesday, the Russian Emergency Situation Ministry said the search zone in Egypt had expanded to 40 square kilometers. Previously, Egyptian authorities said the search zone spanned 20 square kilometers.
The victims
The disaster claimed the lives of 209 Russians, four Ukrainians, one Belarusian and three others whose citizenships were not clear.
At least 25 children were on the plane. Russian media said the tragedy also created a large number of orphans because many parents left their children behind to go on vacation to Sharm el-Sheikh.
So far, 33 of the 224 bodies have been identified, TASS reported Wednesday. The first body has been released for a funeral.
The radar
Flight 9268 was on its way from the Egyptian resort of Sharm el-Sheikh to St. Petersburg early Saturday when it dropped off radar about 23 minutes into the flight, Egyptian officials say.
Air traffic controllers apparently didn't receive any distress calls.
The website Flightradar24, which tracks aircraft around the world, said it had received data from the Russian plane suggesting sharp changes in altitude and a dramatic decrease in ground speed before the signal was lost.
Satellite data
A US military satellite detected a midair heat flash from the Russian airliner before the plane crashed Saturday, a US official told CNN.
Intelligence analysis has ruled out that the Russian commercial airplane was struck by a missile, but the new information suggests that there was a catastrophic in-flight event — including possibly a bomb, though experts are considering other explanations, according to US officials.
Analysts say heat flashes could be tied to a range of possibilities, including a bomb blast, a malfunctioning engine exploding or a structural problem causing a fire on the plane.
Black boxes
Egyptian officials have said they are finishing fieldwork first, and then will go on to investigate the data in the black boxes. Experts started retrieving data from the recorders on Monday, Egypt's Civil Aviation Ministry said.
Russia's privately owned Interfax news agency quoted an unnamed source in Cairo as saying the plane's cockpit voice recorder had captured uncharacteristic sounds the moment before the flight disappeared.
It cited the source as saying that an "unexpected' and "nonstandard (emergency)" occurred "instantly," which was why the pilots failed to send an emergency or alarm signal.
A top Russian aviation official has said the plane broke apart in midair.
Russian state media has reported that so far, investigators haven't found any traces of explosive devices in the debris.
The security situation
Sinai has been a battleground between ISIS-affiliated militants and Egyptian security forces in recent years. Hundreds have died in the fighting.
The militants appeared to claim responsibility for bringing down the Russian passenger jet in a statement posted online Saturday, but officials in Egypt and Russia have disputed that claim, saying there's no evidence to support it.
Egypt's Interior Ministry said it wasn't stepping up security in Sharm El-Sheikh or at the resort city's airport "because there is no indication (the plane crash) was a terrorist operation."
But the U.S. Embassy in Cairo has sent a security message to its employees, instructing them not to travel anywhere in the Sinai Peninsula pending the outcome of the crash investigation.
