Spoken dialogue interfaces are gaining increased acceptance in a wide range of applications. Most current examples of such systems, however, rely on using restricted language and scripted dialogue interactions. We argue that speech interfaces in highly stressed or cognitively overloaded domains, i.e. those involving a user concentrating on other tasks, call for more flexible dialogue with robust, wide-coverage language understanding. We describe an initial effort at addressing flexible and rich dialogue in a system with a number of features, such as full spoken language understanding, a multi-threaded dialogue manager, dynamic update of information, and recognition of partial proper names.