Runway End Safety Area
I too have not seen recent plans for the proposed extension. However, with regard to Runway End Safety Area (RESA), UK airports will from the end of 2013 come under the new European Aviation Safety Agency (EASA) certification rather than the current CAA Aerodrome Licence (based on CAP 168). EASA places a requirement for 240 metre RESA on such a runway, although there are mechanisms to allow a lesser distance subject to satisfactory safety assessment. Such allowances would normally apply to a legacy scenario, but I think it may be difficult to justify constructing a new extension and not meeting the latest standards. In 2009 MAN met the 240m ICAO 'recommended practice' by reducing the declared distances on 05L-23R, although the pavement length remains the same. It will be interesting to see the detailed plans for BHX, and how the declared distances are made up. A starter extension can be a good way to get additional TORA in the favoured direction, but with a lesser runway strip requirement.