Flight software development and testing has traditionally absorbed a significant part of a mission’s time and monetary resources. This is mostly due to its lack of modularity and excessive coupling to each mission’s particular requirements, which hinders its reuse in future projects. In recent years, modular flight software architectures have emerged to solve this issue and generate more modular and reusable software components for avionics and space applications. NASA’s core Flight System (cFS) is perhaps the most well-known and used framework for this purpose, following an open-source approach. Developing flight applications on top of cFS or any of its alternative frameworks, complying with their interfaces and following their architecture results in more modular, standardized, testable and ultimately reusable applications, reducing the costs of subsequent missions. However, these flight software frameworks can still have a steep learning curve for application developers and mission system engineers, due to its increasing features and somewhat complex software structure. To address this, we have developed the SENER Service Layer API (SSLA), a new software framework that further abstracts the application developer from the underlying software and hardware execution platform. In addition to this enhanced abstraction, SSLA has been designed to cover other necessities of flight software development. For instance, it provides an innovative feature that supports native integration of FPGA cores and their access from the software applications. This makes it especially appropriate for its use in projects that use SoC processors with integrated FPGA fabric, greatly helping the process of allocating functionalities to FPGA cores or software applications depending on the mission requirements. SSLA not only includes the abovementioned features built into its API, but also facilitates software creation in a more pragmatic way by providing a development and testing environment specifically tailored for it. In this paper we present the SSLA framework, introducing its features and its integration into a complete avionics execution platform. A quantitative analysis of its performance and some software-related metrics are presented based on a representative application use case.