Last night, the FAA issued an emergency airworthiness directive for Boeing's 787 Dreamliner, after a battery malfunction led an All Nippon Airways flight to make an emergency landing.

The FAA review will cover the design and manufacturing of the aircraft, and focus on its battery, which is believed to be the source of a fire in a parked Dreamliner last week in Boston.

To deliver improved fuel economy, a key upside of the 787, Boeing uses a powerful lithium ion battery and five times more electricity and electrical systems than other jets.

The Dreamliner is the sole plane to use this kind of battery as its primary backup power source, according to Wired, and the FAA only certified its use under several "special conditions."

Lithium ion batteries generate more energy than other types of batteries, which is why Boeing chose to use them. But they tend to overheat, causing "thermal events" — like fires — according to Rick Newman at US News.

University of Dayton professor Raul Ordonez told CNN, "These kinds of batteries are slightly more likely to cause problems."

Dr. Eric Stuve, a professor of chemical engineering at the University of Washington, told Wired, "These batteries have flammable components, that it well known."

In an airline industry that is struggling to make profits in the face of rising fuel costs, the promise of improved fuel efficiency is the biggest selling point of the Dreamliner,

The big question now is whether the battery troubles are a result of flawed design or manufacturing. A fault in the manufacturing process would be relatively easy to repair.

But if the design of the aircraft is flawed, Boeing would have to go back and make fundamental changes in how the plane is built, likely at a huge cost.

For the time being, all of the 50 Dreamliners Boeing has delivered around the world will remain on the ground until further notice.

Here's a full history of the problems with Boeing's Dreamliner >