Fused Filament Fabrication (FFF) technology is increasingly applied in automotive, aerospace and medical applications. FFF is one of the most widely used additive manufacturing techniques to manufacture thermoplastics or their composites. FFF enables improvement in both cycle time and total cost of product development. Such improvements are achieved through the quick manufacture of functional prototypes enable real-world product development and testing. While the benefits of FFF are undeniable, its use in demanding applications is hindered by materials properties. The used commodity and standard polymers actually exhibit low to medium thermal and mechanical properties. To overcome this limitation, the aerospace industry looks for high-performance thermoplastics to obtain plastic parts strong enough to be used as a replacement for metal. Recent developments in FFF equipment now enable engineering polymers, such as Polyether ether ketone (PEEK) and Polyether imide (PEI), to be utilized for parts with increased mechanical and thermal properties. Thus, this article reviews and discusses the properties and the printing parameters of PEEK and PEI produced by FFF.