Apparatuses, devices and systems for attaching seatbelts to anchoring structures in aircraft and other vehicles, are described herein. In some embodiments, such apparatuses include a modular connector having a base configured to be attached to an anchoring structure, a body configured to be attached to a seatbelt, and an annular lock configured to releasably couple the body to the base. In these embodiments, the body carries the lock adjacent to an aperture configured removably receive the base. When the body is pressed over the base, the base passes into the aperture and contacts the annular lock, expanding the lock outwardly around the base. The base continues moving though the aperture in the body until the lock retracts into a groove in base, thereby releasaby locking the body to the base.