For more than two decades, the EU has been supporting free transnational access (TA) to existing national research infrastructures (RI). In particular, the optical/infrared and the advanced radio astronomy communities are now recognised as TA flagship communities. Their telescopes and instrumentation complement each other with respect to wavelength coverage, as well as spectral, spatial and time resolution, and therefore together form a cohesive suite of RIs that made ground breaking discoveries possible and thus strengthened Europe's leading role in international science. While scientists more and more rely on multi-wavelength and multi-disciplinary access to the best RIs, there is a quest by the RI providers for a sustainable funding scheme for TA, since establishing and maintaining outstanding RIs requires considerable resources. In this pilot, the best research institutions from both communities will combine their efforts to further improve and harmonize their services and to make best use of their RIs, allowing mutual and TA to telescopes, telescope networks, and data archives. This will facilitate multi-wavelengths and time-domain studies. TA shall be simplified by the development of a common proposal submission tool. Improved instruments, adaptive optics, and software to deliver science ready data products will boost the performance of our RIs. This pilot will address imminent threats to astronomical research from satellite mega constellations and commercial radio emitters, and finally, it will develop plans for a long-term mutual relationship and for a continued funding of TA beyond this pilot.