The challenges of information systems (IS) development have changed significantly in the past 15 years. From a situation where the main problem was to build stable systems based on a requirements specification, the IS project manager now faces challenges of integration; for example: how to integrate a new information system into large existing information infrastructures and unstable business processes? Building on a socio-technical perspective, four types of integration were identified and analyzed: external and internal stakeholder integration, and internal and external technical integration. A longitudinal case study of an e-business development project in the airline industry identified and highlighted some managerial challenges of integration. Findings include: Internal technical and (to some extent) stakeholder integration is well supported by traditional project management techniques and software engineering frameworks, such as the Rational Unified Process (RUP). However, the challenges of external stakeholder and technical integration is underrated in IS development research, and not well supported in RUP.