5 Things to Know This Morning

— -- Your look at five key stories related to Thursday's downed Malaysia Airlines plane over Ukraine.

1. Malaysia Airlines Tragedy an 'Outrage Against Humanity'

The pro-Russian separatists who control the area where a Malaysia Airlines flight was brought down agreed today to allow investigators safe access to the site to recover bodies and gather evidence, according to a statement from the Organization for Security and Co-operation in Europe.

It was unclear how soon investigators would begin sifting through the charred wreckage of the airliner, which was carrying 298 people when it went down Thursday in Ukraine near the Russian border. The plane had left Amsterdam at 12:15 p.m. (local time) and was estimated to arrive in Kuala Lumpur International Airport Friday at 6:10 a.m. (local time), according to Malaysia Airlines.

FBI and NTSB officials will head to Ukraine in an "advisory role" in the investigation, a senior administration official told ABC News.

2. 'Bodies Scattered Everywhere,' Witness Says

A witness on scene of the downed Malaysia Airlines plane in Ukraine described the sight as "grim" and said there are "bodies scattered everywhere."

"There's blood splattered everywhere, and pieces of remains," said John Wendle, a freelance reporter for ABC News. "It's a pretty grim sight. ... This is terrible."

3. What Actually Happens When a Missile Strikes a Plane

People aboard Malaysia Airlines' doomed Flight 17 would have had no idea a missile was coming -- and no way to prevent it, experts said.

The explosion captured in a video likely didn't happen until the Boeing 777 aircraft crashed into the ground, Timothy Holt, a professor at Embry-Riddle Aeronautical University in Daytona Beach, Florida, told ABC News.

"In this case, it looks like most of the aircraft disintegrated upon impact [with the ground]," he said.

4. Why Airlines Didn't Avoid Risky Ukraine Airspace

The possibility that the civilian jetliner downed over war-torn eastern Ukraine with nearly 300 people on board was hit by a missile could have profound consequences for the world's airlines.

Airlines might have to be more vigilant about avoiding trouble spots, making flights longer and causing them to burn more costly fuel. They may even be forced to reconsider many international routes.

In the hours after Thursday's disaster involving a Malaysia Airlines jet, carriers around the globe began rerouting flights to avoid Ukraine. Some had been circumventing the country for weeks. Experts questioned the airline's decision to fly near the fighting, even as Malaysia's prime minister said that the plane's route from Amsterdam to Kuala Lumpur was declared safe by international aviation authorities.

5. Double Disasters Taint Malaysia Airlines

Hit by two astonishing tragedies in quick succession, the Malaysia Airlines brand may become the airline industry's equivalent of asbestos or News of the World: toxic to the public and, experts say, impossible to redeem.

Malaysia Airlines Flight 17 was downed over eastern Ukraine Thursday with 298 people aboard by what American intelligence authorities believe was a surface-to-air missile. Just four months earlier, a Malaysia Airlines jetliner carrying 239 people disappeared about an hour after taking off from Kuala Lumpur. The jet has still not been found, a source of profound unease for travelers and the aviation industry.

"I can't comprehend of anything they can do to save themselves," said Mohshin Aziz, an aviation analyst at Maybank in Kuala Lumpur, Malaysia.