From the UK Mats Part 1 (Cap493):
Division of Airspace
The United Kingdom airspace is divided into two flight information regions. Within each region the airspace below flight level 245 is known as a lower flight information region (FIR) and that at and above as an upper flight information region (UIR).
---basically in the UK, the airspace above FL245 is Class B, therefore everyone has to have a clearance to enter and thus is known traffic. In many parts of Europe the division is FL195. Inside FIR's, Airways and Advisory routes are established, and in the UIR's these are then Upper Air Routes. An Airway is 10nm wide, extending 5nm either side of the centreline, often (but getting rarer) outside these limits you are outside CAS. In UIR's you are always inside CAS, and if you get over 5nm from the centreline of an Upper Air Route, are only considered to be 'off route' whereby co-ordination with the Military is normally necessary. In the UK there are set times where all a/c will be given on-route status even if off route, normally during the night and at weekends. Not every Airway has an associated Upper Air Route and vice versa.
Classification of Airspace
The classification of the airspace within a flight information region determines the flight rules which apply and the minimum services which are to be provided.
---the classes are A-G, A-D being controlled classes, E/F are advisory areas, and G is totally uncontrolled.
CTA-Control Area
CTR-Control Zone
---CTRs are control zones within defined limits of an aerodrome, and these can be surrounded by CTAs (Control Areas) to link to the Airway network and give added protection if necessary.
In the abbrieviation list there is no mention of UTA.
Hope this helps - 5mb.
