1. Part of airspace above a variable vertical limit.
2. controlled airspace used mainly by jets in the cruise flight phase.
1. EUROCONTROL (2005) Glossary for Flight Statistics & Forecasts, v1.0 
2. EUROCONTROL/EUROPEAN UNION (2009) EPISODE 3 - Single European Sky Implementation support through Validation, D2.4.3-04 - Method for Systematic Risk Assessment for Units of Operation, V. 1.01
In Europe, the Upper Information Region (UIR) is defined as airspace above a division level (generally FL195). It may vary in different countries. Maastricht Upper Area Control Centre (MUAC) covers airspace above FL245 in Belgium, the Netherlands, Luxembourg and NW Germany. In the USA, UIRs are not used, but high altitude en-route sectors typically begin at FL240. Upper airspace is controlled through area control centres (ACC) in Europe or ATC centres (ATCC) in the USA. Categorisation varies, e.g. Class C in most of ECAC; Class B in the UK until 2006; and Class A in the USA.
EPISODE 3 (see above)