This report is Deliverable 4.2 of USEPE project. The report is a first version of an overall document dealing with the tasks related to the exploration of Machine Learning (ML) for insuring a safe drone’s operation. In this Deliverable 4.2, an extensive literature review is provided. At this stage of the project, there was a need to identify the most suitable machine learning algorithms that will serve the USEPE project. Analysis of existing works related to machine learning within the aviation industry is as well presented. The literature review identified a wide variety of ML algorithms and quality metrics that are described in this report. At this stage, the use of the unsupervised ML is promising as it is designed to be flexible, efficient, intuitive, and integrated seamlessly.