Requirements engineering is a creative process in which stakeholders and designers work together to create ideas for new systems that are eventually expressed as requirements. This paper describes RESCUE, a scenario-driven requirements engineering process that includes workshops that integrate creativity techniques with different types of use case and system context modelling. It reports a case study in which RESCUE creativity workshops were used to discover stakeholder and system requirements for OMAN, a future air traffic management system for managing departures from major European airports. The workshop was successful in that it provided new and important outputs for subsequent requirements processes. The paper describes the workshop structure and wider RESCUE process, important results and key lessons learned.