From Nature:

Researchers from MIT have flown a plane powered by an ‘ion drive’ for the first time. The drive uses high powered electrodes to ionise and accelerate air particles, creating an ‘ionic wind’. This wind drove a 5m wide craft across a sports hall. Unlike the ion drives which have powered space craft for decades, this new drive uses air as its accelerant. The researchers say it could power silent drones.

Check out this video featuring Steven Barrett, the researcher who led the team:

This first flight made it about as far as the Wright brothers' first flight at Kitty Hawk. While it seems infeasible for passenger flights, it does have the potential to create a new class of small, silent, and clean drone aircraft.