Plasma actuated Aircraft

 Some researchers published video showing plasma pulsed aircraft; mechanism of the thrust generation is similar to the plasma actuator shown below. 

 http://jaesan-aero.blogspot.com/2017/11/plasma-thrust-generator-in-atmospheric.html

 Although it has a lot of task to be a practical aircraft, that kind of propulsion become efficient at the high altitude because of smaller breakdown voltage of the atmosphere. 

 Indeed, there will be a potential for HALE type aircraft without mechanical moving part if solar panel could provide enough power for them.