what everyone is asking about AirAsia?

1. What happened exactly?

Some basic facts are known about Flight 8501's journey before it lost contact with air traffic control.

• The Airbus A320-200 took off from the Indonesian city of Surabaya at 5:36 a.m. local time Sunday with 155 passengers and 7 crew members on board. Its destination was Singapore, a journey that usually takes a little over two hours.

• At 6:12 a.m., one of the pilots asked air traffic control permission to turn and climb to a higher altitude to try avoid bad weather, according to Indonesian officials.

• Minutes later, the plane disappeared from air traffic control's radar.

• At 7:55 a.m., Flight 8501 was officially declared missing. Its last known position was over the Java Sea, between the islands of Belitung and Borneo.

• The majority of those on board the plane are Indonesian. There are also people from South Korea, Britain, France, Malaysia and Singapore.

But beyond those points lies a huge amount of uncertainty.

2. If the pilots requested a higher altitude because of weather, why didn't air traffic control provide an alternative path?

Air traffic control approved the pilot's request to turn left but denied permission for the plane to climb to 38,000 feet from 32,000 feet, Djoko Murjatmodjo, an aviation official at the Indonesian Transport Ministry, told the national newspaper Kompas.

The increased altitude request was denied because there was another plane flying at that height, he said.

Djoko suggested that Flight 8501 ascended despite air traffic control denying it permission.

3. Could it have been a terrorist act?

With uncertainty over what exactly happened to the plane, theories about what happened are proliferating. But officials haven't so far suggested there was any foul play aboard Flight 8501. A clearer picture is likely to emerge once the plane is found.

One expert offered CNN a less sinister theory about what might have happened: The plane stalled mid-flight.

A screen grab purportedly leaked by an Indonesian air traffic controller appears to show that Flight 8501 was rising in altitude but was losing speed at a velocity that was too slow to sustain flight, said Geoffrey Thomas, managing director at the aviation industry site airlineratings.com.

The data taken from the screen grab comes from an Indonesian pilot who was given the screen grab anonymously by an air traffic controller who had been tracking the flight, according to Thomas.

Thomas added that the typical procedure for a pilot is to push the nose of the plane down to gain airspeed and exit the stall, but in very rare circumstances atmospheric conditions can make that impossible, leading to a situation that is not recoverable.

4.  How is this similar to the disappearance of Flight MH370?

Superficially, yes, there are similarities with Malaysia Airlines Flight 370, which disappeared in March: A passenger jet flying over Southeast Asian waters in the early hours of the morning drops off radar, prompting a huge international search.

But analysts say there are several noteworthy differences.

In MH370's case, the pilots made no radio transmissions about the plane's mysterious change of course, deepening the puzzle about what happened. But one of the Flight 8501 pilots told air traffic control what he wanted to do -- turn and climb to avoid bad weather.

The AirAsia flight is believed by Indonesian officials to have gone down into the Java Sea, a much shallower and busier body of water than the southern Indian Ocean, where MH370 is thought to have ended up.

Finding Flight 8501 will almost certainly be much easier than the still ongoing hunt for MH370, said Steven Wallace, former director of the Federal Aviation Administration's Office of Accident Investigations.

It's "very unlikely that we're going to see anything remotely close to what we saw with Malaysia 370," he said.

5. Is it something about Asia that makes air travel unsafe?

It's been a year of several high profile and deadly air disasters -- three of them linked to Malaysia. But experts says the skies are still safe.

This year has had the lowest number of crashes since the late 1920s, according to Geneva-based Bureau of Aircraft Accidents Archives.

This year's number of crashes at 111 is down from 139 last year, says the bureau, which defines an air accidents as "any event where aircraft suffered such damage that it is not in a position to be used anymore and that it is removed from service."

But there is bad news too. If everyone aboard Air Asia is dead, the number of fatalities in 2014 will reach with 1320, the most since 2005, when 1,463 people died.

Asia has had a particularly bad year. Experts admit it's strange that Flight 8501 should have dropped off radar in the same region of the world as MH370.

"It's eerie, it's unusual or just kind of spooky that this would happen in this area, but we don't know the facts yet," said Peter Goelz, former managing director of the U.S. National Transportation Safety Board.