The traditional 1–11 numbers have been worn on occasions by English clubs since their respective leagues introduced squad numbers. Premier League clubs often used the traditional squad numbering system when competing in domestic or European cups, often when their opponents still made use of the traditional squad numbering system. This included Manchester United's Premier League clash with Manchester City at Old Trafford on 10 February 2008, when 1950s style kits were worn as part of the Munich air disaster's 50th anniversary commemorations.