Remains of Russian plane crash victims arrive in St. Petersburg

An emergency ministry plane with the remains of 144 victims of this weekend's Russian airliner crash in Egypt arrived in St. Petersburg, Russia's second largest city, early Monday morning.

Investigators have not said whether the crash, which killed all 224 people on board, occurred due to a malfunction with the plane, an act of terrorism, or another reason. The plane broke up in midair over Egypt's troubled Sinai peninsula, where Islamic militants are waging a violent insurgency campaign.

In St. Petersburg, two white trucks ferried the remains of the passengers of Kogalymavia Flight 9268 from the tarmac to a city crematorium for identification by relatives. The government of St. Petersburg extended an official period of mourning through Monday, and makeshift memorials have appeared at the city's main Pulkovo airport.

In Russia, the crash is being called the deadliest aviation disaster in the country's history.

The repatriation of the remains came as Russian labor officials said Monday that Kogalymavia, the airline managing the charter flight, had not paid its employees in the last two months due to financial difficulties.

"The size of the debt is being assessed," the press service for Rostrud, Russia's Federal Labor Agency, wrote in a statement. Russian airlines are in severe financial distress because of the country's economic crisis, and Transaero, Russia's second biggest airline, was grounded after filing for bankruptcy this month.

Russian charter and domestic airlines have long had a spotty safety record, and a pilot on the flight complained to his wife about the condition of the Airbus 321-200 shortly before take-off, Russian state television reported.

However, the pilot did not send an SOS signal before the crash, Egyptian Civil Aviation Minister Hossam Kamal said, and the plane broke up in midair, spreading debris over seven square miles, according to a senior Russian aviation official on a visit to the crash site this weekend.

Modern planes do not usually fall apart in flight, barring an explosion caused by a bomb or missile, but Viktor Sorochenko, an official with Russia's Interstate Aviation Committee, said it is too early to tell what caused the crash.

The plane crashed in a remote area of central Sinai, a large desert expanse where Islamist militants are waging a violent anti-government insurgency.

The crash occurred just weeks after Russian warplanes began targeting rebel positions in Syria, and the Islamic State's Sinai affiliate was quick to seize the opportunity to declare that it had shot down the plane in retaliation.

Both Russian and Egyptian officials have denied claims by the Islamic State militant group that it had downed the plane, however.

Still, Russian Transport Minister Maxim Sokolov said Sunday it was unclear why the plane suddenly, rapidly fell from roughly 31,000 feet shortly after take-off Saturday from the Egyptian resort town of Sharm el-Sheikh.

Sokolov arrived in Egypt with a team of experts to help with the investigation but said "little information" had been gathered so far, the Reuters news agency reported.

Egyptian officials said the Civil Aviation Ministry was analyzing data from two recovered flight recorders now at the ministry headquarters in Cairo.

Four major international airlines and a regional carrier announced they would avoid flying over Sinai until investigators know what caused the crash of Flight 9268. The move by Lufthansa, Air France-KLM, Qatar Airways and the Dubai-based Emirates and FlyDubai airlines to divert flights from Sinai's airspace underscored growing international concerns about the jihadists' reach in the region.

The only U.S. airline that flies in the region, United, does "not see a need" to change its routes at this time, a spokesman said Sunday.

Germany's Transportation Ministry urged the country's airlines not to use the route the Russian plane was flying when it crashed, according to the Associated Press. Before the crash, the ministry had issued a warning to airlines about flying over the northern part of the peninsula, which is a militant stronghold.

The Islamic State's local affiliate is believed by security experts to possess shoulder-fired anti-aircraft missiles that can hit low-flying aircraft in the area. But those weapons systems are not capable of hitting aircraft above 10,000 feet, analysts say.

In July 2014, Malaysian Airlines Flight 17 was shot down over eastern Ukraine by a warhead fired from a Russian-built Buk missile system, Dutch investigators said. That plane was flying at 33,000 feet after its departure from Amsterdamn airport.

If militants in the Sinai were responsible for the destruction of the Russian airliner Saturday, they could only have done so with the acquisition of a similar sophisticated weapons system - or through the placement of a bomb while the plane was still on the ground.

The Egyptian government said Sunday that 163 bodies had been recovered and transferred to three facilities outside Sinai. Some of the bodies were repatriated to St. Petersburg, the flight's destination, Sunday, officials said. Hundreds of mourners bearing flowers and stuffed animals gathered at Pulkovo Airport.

The charter flight operated by the Russian carrier Metrojet disappeared from controllers' radar 23 minutes after take-off from the beach resort of Sharm el-Sheikh, a popular destination for Russian tourists, Russia's Federal Air Transport Agency said. It was carrying 217 passengers and seven crew members, the Egyptian Civil Aviation Ministry said.

Among the passengers killed were four Ukrainian nationals and one Belarusan. The remaining passengers were Russian citizens, including 17 children, authorities said.

A terrorist attack on a plane full of Russian vacationers could dampen the enthusiasm of the Russian public for the Kremlin's intervention in the Syrian civil war, although past terrorist attacks within Russia itself have generally led to increased support for the government.

Russian officials announced Saturday that they had opened an investigation into potential safety violations by the airline. The Investigative Committee launched an immediate search of the airline's offices in Moscow and its facilities at Domodedovo International Airport, southwest of the capital.

Over the past few decades, there have been a handful of cases of catastrophic failure while planes were aloft. In 2002, a Boeing 747 flown by China Airlines broke up in flight, killing 225, and metal fatigue was blamed. In 1985, a Japan Airlines plane, also a 747, crashed when a rear bulkhead blew out. Investigators pointed to a faulty repair job. In that accident, 520 were killed.

The Metrojet Airbus was built in 1997 and had more than 56,000 hours of flight time, according to the Airbus company.

The southern Sinai, far from militant activity near the Gaza Strip, has long been a favorite destination of Russians on package tours, with its warm waters, attractive beaches and low prices. Winter is the peak tourist season, and according to reports, several thousand Russian vacationers are there now. Russia has not announced any restrictions on flights to or from the Sinai.

Erin Cunningham reported from Cairo. Heba Habib also contributed from Cairo.

This story was originally published November 2, 2015 at 11:25 AM with the headline "Remains of Russian plane crash victims arrive in St. Petersburg."