Need to improve efficiency in terms of power in to thrust out and thrust per volume. But it was a much more convincing demonstration that the tinfoil triangles floating around YouTube. It takes a lot of power though. Interested to know how they plan on generating that power on an aircraft.
The basic principle is simple enough: ionise air with a high voltage and attract the ions backwards with a second electrode place further back. The ions then bump into more air, drawing it along with them a bit like the Dyson air blade idea. Throwing this wake backwards creates forward thrust.
But efficiency is poor and the MIT model had to be so light that it had no flight control system.
The aircraft designer Seversky built a more controllable flying model around 1960. However it had to be tethered to a heavy off-board high-voltage power supply. There was an informative article published in Popular mechanics: "Major de Seversky's Ion-Propelled Aircraft", Popular mechanics, Vol. 122, No. 2, August 1962, pp.58-61, 196. https://books.google.co.uk/books?id=ROMDAAAAMBAJ&pg=PA58
I remember that the odd science fiction story picked up on the idea.
However its development has been hampered by several problems. Besides low efficiency, there is also a need for electrical safety. As significant, I would suggest, was a tendency in the past to focus on VTOL performance, in the form that is nowadays termed "powered lift", as it requires an order of magnitude more efficiency in thrust generation than conventional aerodynamic flight. Seversky's model being a case in point.
You can waste a lot of power turning a high-voltage electrical current into an air current and most research goes into trying to improve conversion efficiency through variations in electrode geometry. Also, the larger the volume of air you move, the slower you need to move it and the higher your efficiency (hence the huge fans on jet airliners). So a whole-wing EHD system is attractive. But rain stops play. It draws the charge out of the air, falls away with it, and the thrust dies. So any practical design must be enclosed in a water-shedding duct, perhaps like the dust-filtering vortex intakes fitted to helicopters in the desert. And that makes a whole-span installation next to impossible to engineer.
Another big problem with a practical system is corrosion. Ions are corrosive beasts. In a previous life I built power supplies for them to them to etch away silicon chips. However on an EHD drive they eat away at one or both of the electrodes instead. The more you crank up the power to useful levels, the faster your electrodes corrode. This was the problem that sounded the death knell of the electromagnetic rail gun.
Unless they can increase both conversion efficiency and power density by an order of magnitude, the idea can never really take off.