All civil aviation authorities around the world publish technical information required for using their airports and routes in the form of Aeronautical Information Publications. These include details ranging from runway lengths and surfaces to operating hours and fire-fighting equipment; cruising levels to waypoint identifiers.
Eurocontrol are co-ordinating the electronic publication of AIPs using XML. eAIPs are classic examples of documents suited to XML markup: highly structured documents which may need their contents manipulating in various ways.
Together with Helios Technology, I worked on a user requirements analysis and prototype website for publishing XML-sourced eAIPs on the Internet.
In the course of this, I became very impressed with the power of XML and the possibilities it offers, through XSLT stylesheets, of alternative presentations and manipulations.