Slovakian firm AeroMobil plans to finalize its flying car design and begin accepting deposits in 2017.

PAL-V from the Netherlands has already begun taking orders for its vehicle, and expects deliveries to begin in the spring of 2017.

And California-based Moller International has begun accepting deposits and says it could begin selling its flying vehicles next year, provided the U.S. Federal Aviation Administration grants the necessary regulatory permissions.

These firms all have high hopes for the future, but various major roadblocks could keep them from reaching their near term goals.

Many companies have previously predicted they'd start selling their vehicles in a year or two, only to delay their plans again and again.

As it stands, regulators are the main reason flying cars are kept off the roads and out of the skies.

The vehicles have to pass numerous tests to prove they're road ready and fit to fly. Getting all the necessary aviation, road and transportation certifications can take ages.

"Building something that works is different than [building] something that's allowed," said Robert Dingemanse, CEO of PAL-V, who said his gyrocopter-style vehicle meets all the necessary road and air regulations in Europe and the U.S.

While these regulations may seem like a hindrance to the casual observer, they are designed to keep everyone safe in the air and on the ground.

Case in point: In early May, the AeroMobil 3.0 prototype crashed during a test flight. The pilot was unharmed, but the situation clearly demonstrates the importance of careful regulation and strict safety certifications.