A day after two Russian airliners fell from the sky, confusion over what happened reflected a country torn between skepticism that the government would tell the truth and concern about an airline industry so old and poorly maintained that two planes might go down by accident at the same time.

Both main theories about the crashes were nearly unbelievable.

According to one, the two planes carrying a total of 90 people crashed almost simultaneously because of technical malfunctions or human error, a mathematically unlikely variant suggested by government investigators as they examined the wreckage.

But many politicians, airplane engineers, passengers and everyday Russians were quick to assume that the crashes were not a stunning coincidence. In their far more widely held version of events, Chechen separatists pulled off something like a Russian Sept. 11, capturing two planes with military-like precision and bringing them down days before a government-rigged election in the separatist republic.

By late Wednesday, there was no firm public evidence either way, and President Vladimir Putin, often quick to blame terrorists when mysterious mayhem occurs, offered condolences, not explanations.

"The first thought is that this is 9/11 in Russia," said Alexei Venediktov, chief editor of the independent news radio station Echo Moskvy, "and that the government cannot acknowledge anything like a terrorist act comparable to 9/11."

Venediktov and others pointed to Sunday's presidential election in Chechnya as the likely trigger for the crashes. "To admit this is more than a weird accident would be to admit defeat in their war on terrorism," he said.

Vladimir Ryzhkov, an independent member of parliament, said he, too, found the official statements difficult to swallow.

"It's very hard to believe two planes can crash at the same time. It's hard not to believe it's not a terrorist act," he said. "Why would the authorities not say that? Because every year under Putin there have been more terrorist acts and more victims. That means that under his leadership Russia is a less safe country, and the president and the authorities don't want to admit it."

Recent opinion polls suggest that the government may have a hard time convincing the public of its version of events, whatever it ends up being. Although Putin is trusted by 68 percent of Russians, his government is extremely unpopular, with 60 percent of those surveyed disapproving of its actions in a poll this month by the independent firm Yuri Levada's Analytical Center.

"We have a strange situation -- people believe the president is good and the government is bad, even though the president appoints the government," Ryzhkov said. "It's hard to believe, but in Russia it happens."

In recent years, Russia has gone through more than its share of hard-to-believe tragedies, followed by official explanations that the public viewed with skepticism.

In 1999, the Federal Security Service, once headed by Putin and the domestic successor to the KGB, blamed Chechen rebels for a series of deadly apartment bombings that helped trigger the current round of hostilities in Chechnya. But the FSB never produced definitive proof, and conspiracy theorists to this day suggest that the FSB itself may have launched the attacks.

After the Kursk nuclear submarine sank in 2000, killing everyone aboard, officials initially said that a foreign sub had collided with the Kursk, a theory never backed up by fact or widely believed. The government later formally blamed the disaster on an explosion caused by leaking torpedo fuel.

And the government has never given its version of how Chechen rebels managed to seize a Moscow theater in 2002, or what knockout gas it used in storming the theater. The gas killed more than 120 hostages.

"The fact there are multiple plausible scenarios speaks to the complicated situation in Russia," said Fiona Hill, an expert on the North Caucasus region at the Brookings Institution in Washington. Her initial reaction, like those of many people here, was to think of terrorism. But as Wednesday's developments unfolded, Hill and others were taking seriously theories that ranged from a fight among organized crime factions to a commercial dispute.

"One thing we've realized today is that to make something look like a terrorist act is easy," she said.

Russian aviation experts were still considering the possibility of a spectacular technical or human failure causing both crashes. It "cannot be excluded," said aviation engineer Oleg Panteleyev, but it would be so unprecedented as to stretch the imagination.

Given that, Panteleyev, currently editor in chief of a specialized Web site for Russian aviation, said that he, too, wondered whether the more believable terrorist scenario was being discounted. "The official bodies are not interested in presenting it as a terrorist act," he said. Panteleyev offered a business twist on why they might be discounting that explanation: "It could damage the business of passenger transportation if they admit it. If they show it's just an accident and the possibility of it being repeated is almost zero, that would calm down the passengers."

At Domodedovo Airport, the departure point for both flights and a busy hub for domestic and international flights, most passengers appeared to be focusing on the normal daily bustle, shrugging off the crashes and the possibility that air travel in Russia was either vulnerable to attack or supremely unsafe.

"We have had no cancellations, everything is normal," said Veronika Ovchinnikova, a Sibir Airlines representative handling ticket inquiries. One 33-year-old man, traveling to Germany on a Sibir plane, said his fatalism overrode his concerns about terrorism or airline safety. "Whatever is going to happen will happen," said the man, who would only give his first name, Igor, as he confirmed his reservation. "Yes, I'm flying."

Passenger Yulia Kiyanova was an apparent rarity Wednesday -- a jittery traveler who actually did something about it.

Kiyanova had been booked to go home to the southern Russia city of Krasnodar on what would have been her first flight in 14 years. A reluctant flier, she prefers the train. "I think I will return the ticket and go to the train," said Kiyanova, a toy wholesaler. "I'm going to be late, but I will call my boss and tell him I'm really scared ."