That’s the one I was thinking of, thanks Pushkin.
It’s not that uncommon. Naturally, there’s a list of gaol helicopter escapes on Wiki.
There was one in Australia in 1999. Both the escaping prisoner and his rescuer were later recaptured.
Airspace control is linked to traffic need. Unless a prison is located next to a major airport there aren’t going to be any restrictions around it. Aircraft under VFR flight rules aren’t required to maintain contact with a radar center, or even have a radio or transponder depending on airspace.
It’s not a punishment. It’s for their safety. Famous prisoners are often the targets of murder attempts by other prisoners.
Airspace above prisons is prohibited to overflights below a certain level in New York. I think other states probably have similar laws.
It might fall under the same rules as stadiums. I couldn’t find it on the FAA site but that doesn’t mean it’s not there. There’s a prison near an airport I frequent so I occasionally find myself flying over it alhough I do try to avoid it. I checked a sectional map and it was clearly marked as a prison.
Better tell that to Nite Owl and Silk Spectre.
And a lot of other people as well. The Korydalos prison is situated in a densely populated area.
No one’s yet mentioned Superman II, and Lex Luthor’s escape from prison via helicopter? Classic.
Well, assisting a prisoner to escape is presumably prohibited as well. 
If someone’s willing to break that law, I imagine they’d also be willing to risk the penalties associated with illegal overflight.
Wow, according to that list this is the second successful helicopter escape from the same prison! You think they’d learn their lesson…
Well as a former Correctional Officer at Millhaven Maximum Security Institution in Kingston, Ontario, I am able to comment on this subject with some degree of knowledge.
About 15 years ago there were a rash of attempts like this in Western Canada, so much so, that Corrections Canada National Headquarters issued a memo to every institution in the country.
I remember reading it as I was manning one of the towers because the memo was duct-taped to the gun rack.
I can’t recall word for word what it said, but basically they instructed us that in the event that such a situation took place, we were NOT TO SHOOT DOWN THE HELICOPTER under any circumstances.
One of the reasons was the possibility of the pilot being under duress.
I’m sure a full size helicoptor crashing into the prison yard with everyone outside would also cause a substantial loss of life.
I won’t say a loss of life of ‘innocent people’, but you know what I mean. 
The memo instructed us to shoot them as they were running towards the helicoptor, but once on board, we were to stop shooting once it began it’s lift.
Regards
Gus
Not just the second escape. The second escape by the same people.
There’s a jail in downtown Chicago (I don’t know what it is) that has an exercise yard on the roof, which you can see if you’re on the Observation deck of the Sears Tower and look down. I don’t know if there was ever an attempt to escape by helicopter in the past, but now there’s mesh over the exercise yard.
I’m pretty sure there’s a movie from the '70’s or '80’s which dealt with this scenario. I think that Charles Bronson played a part.