One of the main drawbacks for hybrid-silica aerogels is their flammability, an inherent property of the organic groups which severely limits their potential. This research is an important step to produce viable aerogels and take advantage of their low thermal conductivity and very low density, for example as lightweight insulation material used in aircraft cabins or other vehicles. Within this work, three different flexible hybrid-silica aerogel systems with different shapes and densities were investigated towards their burn behavior before and after soaking with the flame-retardant triphenyl phosphate (TPP). For this, different concentrations and evaporation temperatures were used before ultimately burning the samples while tracking the duration of the different fire stages. This data was used to calculate their flammability and overall performance for lightweight application in airplanes. In addition to this, other pre- and post-burn analysis like IR, TGA or melting behavior were performed. In the end, we were able to produce promising samples with good flame-retardancy at only minimal increase in density, an overall key combination useful for many different applications.