The main focus of Planning and Scheduling (P&S) research is centred around the construction of solver engines, which accept a domain (and task) model as input, and output solutions to P&S problems. This research is beginning to lead to the widespread use of the technology, and P&S solvers can be found embedded in a number of application areas, including control of UAVs, story narrative generation, Web service composition, and logistics. The domain models for these applications are created to contain knowledge such as the physics of the actions, the objects affected by the actions, and the goals or tasks that require solving. The focus on the solver engine needs to be complemented with research on the construction, validation, and optimisation of domain models and domain model languages, such as PDDL (Planning Domain Definition Language). Interest in knowledge engineering (KE) for P&S therefore has grown in recent years, and is concentrated on the formulation of application knowledge bases and the fusion of them with planning engines to create operational systems. Although the main aspect of KE is in domain modelling, it also includes the areas of heuristic acquisition, planner-domain matching, domain knowledge validation, and so forth.We can categorise methods of producing domain models containing representations of actions, ready for use in a solver, into two main areas:1. Handcrafted method: a user builds up a model from scratch, perhaps aided with the use of knowledge acquisition tools. In this case, the user needs to be an expert in the domain model language that the solver accepts. 2. Automated method: a user creates or obtains a model in an application-oriented language, and a translator or learning algorithm inputs the model in the application language and outputs solver-ready domain models. The input model could range from being in the form of a declarative formal specification, to a set of example plan scripts.Over the last 40 years in the development of P&S, domain models have been produced in the main using method 1. An important aspect, relevant for the progression of the field of domain independent P&S, is that general solver engines can be accessed and used by non-AI (artificial intelligence) experts. The development of tools and techniques within method 2 furthers this aim, and overcomes the need to handcraft domain models, which is seen by some as a limiting factor in the deployment of P&S. This recognises that experts in that area may be familiar with their own description languages, but not with P&S description languages such as PDDL. It holds the promise that P&S solvers could be embedded into tool support in the application without the need for a planning expert.This special issue contains the selected and extended papers of some of the competitors from the third competition on KE for AI P&S systems (International Competition on Knowledge Engineering for Planning and Scheduling (ICKEPS)), held during ICAPS, the International https://www.cambridge.org/core/terms. https://doi