It's one of science fiction's greatest unfulfilled promises, right up there with teleportation and time travel.

And, no, Terrafugia hasn't built us a Tardis or promised to beam us up. But they say they're closer than ever to giving us a flying car.

This week, the Woburn, Massachussetts-based aerospace company announced it has begun feasibility studies on a car capable of vertical takeoffs and landings. The TF-X would be a four-seat, plug-in hybrid electric vehicle, according to the company.

“We are passionate about continuing to lead the creation of a flying car industry and are dedicating resources to lay the foundations for our vision of personal transportation,” Terrafugia CEO Carl Dietrich said in a media release. “Terrafugia is about increasing the level of safety, simplicity, and convenience of aviation.  TF-X is an opportunity to provide the world with a new dimension of personal freedom!”

Lest you think  the company is just getting our hopes up for some cheap publicity, know this - they've already created a flying car of sorts.

The Transition is a street-legal vehicle that's designed to fly in and out of airports. It was successfully flown for the first time in 2009. The second-generation version of the Transition performed a driving-and-flying demo last year.

The new TF-X project comes as work on the Transition shifts "from research and development to certification, production, and customer support activities," the company said.

Terrafugia says it has about 100 orders for the Transition, which goes for $279,000.

The big difference between the Transition, which is scheduled to hit the market in 2015, and the new flying car is that the TF-X would be able to take off anywhere,  like a helicopter, and not just at an airport.

Its automation systems would make taking off and landing a self-driving process, though the driver would be able to take over manual control at any time.

Terrafugia (Latin for "escape from Earth") says it has had "preliminary conversations" with the Federal Aviation Administration about the TF-X and that the agency has "demonstrated their willingness to consider innovative technologies and regulatory solutions that are in the public interest and enhance the level of safety of personal aviation."

In other words, we might actually get to ride in one someday.

What do you think? Will we see widespread use of flying cars in our lifetimes? Let us know in the comments.