Abstract: The key to the next generation real-time systems is flexible scheduling mechanisms that guarantee hard deadlines and use available spare resources to maximise total system utility. This is a multicriteria scheduling problem. It is argued that common approaches like eager slack usage and mandatory first schemes are not only not optimal but not adequate for a wide class of process models. It is also shown that a late acceptance test model is preferable to an early acceptance test model due to the uncertainty of future behaviour of the system. The discussion is complemented with simulation results.