Two passenger aircraft were involved in a ground collision accident at Buenos Aires-Jorge Newbery Airport, Argentina. Aerolineas Argentinas flight 1478, a Boeing 737-700 (WL), had been cleared to taxi out for departure and leave the platform at exit C. At the same time, Austral flight 2255, an Embraer ERJ-190, had arrived at parking position 26 because no marshaller was present yet at this position, the flight crew stopped the aircraft with the tail section over the taxiway zone. The pilot of the Boeing 737 continued taxiing until the right hand winglet struck the left horizontal stabilizer of the Embraer. Conclusions (translated from Spanish): During a regular air transport flight during the taxy phase to runway 13, the right winglet of LV-CYO struck the left horizontal stabilizer of LV-CIE, due to a combination of the following factors: – Inadequate decision making by the pilot of the aircraft while rolling to exit C, where he encountered another aircraft out of the parking position occupying the taxiway zone and continued rolling with the consequences described above. – Continuing to roll despite exit C was partially blocked with the rear fuselage of LV-CIE, visibly outside the demarcation area (red line). – The position of LV-CIE approximately 13 m before the stop bar in the parking position No. 26. – Absence of a signalmen in the parking position No. 26. – Lack of communication between LV-CIE and ground control, not telling another aircraft was in a position outside the assigned. – Lack of communication between LV-CYO and ground surface to warn that no other aircraft was in a position outside the assigned. – The MOE AU does not specify the action to be taken in case of absence of signalmen at the assigned position on how far should stop the aircraft and how to communicate. – The MOE AR / AU procedures did not foresee the preservation of CVR/FDR in case of accidents/incidents – Visual contamination with elements on the ramp. – Absence of the implementation of the emergency system of Aeroparque. – High workload of the ground controller, which hindered proper control of the movements on the platform. – Opacity of the taxi guide lines in wet conditions. (No refraction by aircraft lights).