Aren't those the three phases of air travel

Landing Zone: That portion of the airport property including the air above which is designed for the actual land-ing and take off of aircraft including the landing strip and adjacent area.

Approach Zone: A trapezoidal area and the air above it which extends outward in a graduated width from the end of the landing zone and may include property consisting of airport property and private property adjacent thereto.

looking at this ref. I'd say the Air Route Traffic Control Center part of a flight could be called the center zone as it's controlled by a center controller

--------------------------------------------------
Note added at 19 hrs 49 mins (2005-11-02 08:12:06 GMT)
--------------------------------------------------

Tom, if this ref. (http://www.dfs.de/dfs/internet/deutsch/default/download/gb20... of the Deutsche Flugsicherung relates to your question, it seems to me that Streckenbereich *does* relate to part of a flightpath; on the site of DFS (Service / Gebühren) you can find that they also collect charges for flights: "Die Streckengebühren werden von der Zentralen Gebührenstelle von EUROCONTROL in Brüssel (CRCO - Central Route Charges Office) als eine einzige Gebühr pro Flug in Euro berechnet und fakturiert. Die Einnahmen werden dann an die Staaten überwiesen (bei uns an die DFS)."

I think the air traffic controllers at EUROCONTROL are exactly the center controllers I spoke about, so the relevant charges relate to this part of any flight. The monopoly your text is talking about most likely refers to the exclusive right of DFS to collect such charges.

I realize that Brie just posted a similar suggestion, but I was really just about to post mine (so I will) and it is a bit different. ;-)

Also see for example: http://vams.arc.nasa.gov/activities/opscons_archive/ons/ONS_...
AND
http://www.google.com/search?hl=de&rls=GGLG,GGLG:2005-22,GGL...
AND
http://www.google.com/search?hl=de&rls=GGLG,GGLG:2005-22,GGL...

--------------------------------------------------
Note added at 22 hrs 10 mins (2005-11-02 10:33:02 GMT)
--------------------------------------------------

I agree with Harry in that I also believe this is referring to a part of the flight itself. After while it may be true that the controllers in charge of guiding the pilots as they fly through this sector are called "center controller" (I think they are also called "en route sector controllers"), but I don't think that the sector is called the "center zone" - I tend more towards "en route sector" (see the second of the links I provided).

For example: "The traffic is subdivided as en route traffic through our area control centres. We have seven of them in the country. Basically, the air space is divided into seven, and the seven centres are responsible for the en route portion. When an aircraft gets near an airport, responsibility for it shifts to a terminal controller, who then shifts it back to a tower controller when the aircraft is within seven miles or five miles, whatever is applicable in the particular case, whether there is radar or not. When they are getting close to an airport, they could be under the control of the tower in that particular case, but the transfer is from the en route sector to the terminal sector, and then to the tower sector." (see http://www.parl.gc.ca/english/senate/com-e/safe-e/02eva-e.ht... ).

--------------------------------------------------
Note added at 22 hrs 14 mins (2005-11-02 10:36:16 GMT)
--------------------------------------------------

Sorry about the mistakes - "After" belonged to a sentence that I ended up changing; and it should read "center controllers". ;-)

--------------------------------------------------
Note added at 22 hrs 17 mins (2005-11-02 10:39:53 GMT)
--------------------------------------------------

Also see: http://www.google.com/search?hl=de&rls=GGLG,GGLG:2005-22,GGL...
;-)