Mid-infrared (MIR) wavelengths offer a critical window for probing these environments. Emission at ∼20 μm traces thermal radiation from warm dust in the inner regions of protostellar outflow cavities and provides access to numerous dust grain and molecular tracers through high-resolution spectroscopy. Despite its scientific potential, the 20µm wavelength range suffers from a lack of high-angular resolution facilities: JWST/MIRI offers exquisite sensitivity at 20 µm but at the cost of low angular resolution and saturation limits that hamper the observation of massive stars; ground-based instruments like COMICS and VISIR giving access to the 20µm bands have been decommissioned or are nearing the end of their operational life without guaranteed replacements; both MATISSE and the future METIS/ELT instrument do not foresee observations beyond 10 µm.

Having access to the ~20 µm Q-band at the VLTI would bridge the gap between ALMA and the current VLTI instrumentation, bringing significant complementarity to the study of the early stages of massive star formation. A possible scope is to investigate whether the combination of ground-based high-angular resolution and ground-based high-spectral resolution across the atmospheric Q band can be enabled through a long-term planning of an infrared interferometric instrument or facility. This talk will outline the scientific objectives achievable with this facility and the observational requirements to address these critical gaps in our understanding of massive star formation, in and outside our Galaxy.