It is 1977 year of a slightly altered history of our world. The Soviet Union has invented, and USA have stolen blueprints (or opposite, USA invented, Soviet Union stole) of a very stealthy flying machine. So, both countries can start mass production of this machines in a few years.
This machines has these properties:
It can be painted in any proper camouflage - the top part can be painted in "summer forest", "autumn forest", "desert". The bottom can be sky blue, gray, or even the pitch dark for operating at night. So, it is not fully invisible, but it is hard to see, as modern camouflaged war machines on good background.
It is 600 kg machine with easy frame, that can carry about 1000kg of weight. Unfolded, it has size of err.... big civil helicopter, folded - it can be stored in army truck.
It has mobility of helicopter - vertical takeoff, can fly in any direction, can even do a barrel roll and withstand few G overloads.
It's speed is up to 300 km per hour (187 miles per hour), while the cruise movement is performed on heights less than 100 meters and speed about 200 km per hour (125 miles per hour).
It flies silently - ordinary human can hear light buzz if the machine fly in few meters just above his or her head.
This machine do not have any light and heat emitting parts like engine nozzles, and it's temperature is only few degrees higher than environment.
This machine costs the same amount as a tank - both USA and Soviet Union can easily build and maintain a few thousand of this machines. Evens wealthy individuals can get one.
This machine can be fully charged from ordinary power socket in few days. And full charge allows it to fly few hours on full speed.
You can install missiles or machine guns on this machine, but it still can carry no more than 1 ton of weight
You can install some light armor on it, but in general this machine is fragile - it can be easily put down with single buck shot from hunting rifle because it propellers' substitutes are big and easy to break. So, with or without armor it is far from flying tank or combat helicopter like Apache or Mi-28.
UPD: This machine is mainly built from radio transparent polymers, it is really hard to be found by radar, especially when it flies below 100 meters following the landscape..
It has compact, high density and unstable batteries, so, well placed shot can set this machine on fire. (Thanks, @JohnDallman)
You can educate helicopter pilots to use this machine in few days.
My idea was to use this machine to silently move paratroopers/spies/saboteurs behind the enemy lines under the cover of the night and as rescue vehicle or use it as a recon craft.
Also it can carry nuclear warheads to enemy territory to be secretly installed and armed for future use.
Unfortunately, i haven't served in army, and i do not know of other uses of such machines.
So, how does this stealthy flying machines can be used in modern warfare?
PS: I do not ask, if this machine is realistic. To build it, we need to invent very efficient engines and motivators for flying machines.