Aerial view of the proposed extension of the VLTI. The new UT5 telescope would be positioned to the southeast of the platform, on the opposite side of the access road. The beam would be propagated to the VLTI tunnel through the J arm of the existing VLTI/AT interferometer, creating four new baselines with north-south orientations, each approximately 200 meters in length. With a length of 220 meters and an orientation at 154 degrees to the South-East, the UT3–UT5 baseline would be almost orthogonal to the existing long UT1-UT4 baseline giving an optimal UV coverage. The long delay line could be obtained by serialising the two remaining, presently unused, VLTI delay lines. Lower pannels: contrast limit of a dual-field interferometer using the current four-UT configuration of the VLTI (left panel), compared to the proposed five-UT configuration (right panel).