Despite the significant success of using Machine Learning (ML) in numerous industrial applications, how to integrate these technologies in safety-critical contexts poses many challenging questions. Several industrial and academic research groups, as well as various standardization committees are actively working to provide (partial) answers to these questions. In this document, we focus on one such initiative led by the EASA, which proposes a series of guidelines and requirements to develop ML-based systems for critical applications in the aviation domain. In this paper we investigate whether these requirements can be satisfied when using ML to solve a relatively simple regression task, that of building a neural network surrogate of the International Geomagnetic Reference Field (IGRF) model. Though we acknowledge all the structuring efforts towards the ambitious certification goal, our analysis pinpoints several important issues with some of these guidelines, such as ambiguous definitions, prohibitive computational costs, or currently very limited theoretical guarantees. Our analysis compels us to remain cautious about the various general recommendations proposed for designing trustworthy ML components for safety-critical systems. These conclusions call for the academic and industrial communities concerned by "Trustworthy AI" to strengthen their collaboration and pursue the research efforts necessary to address the existing challenges and establish sound methodologies for building safe ML-based applications.