Aircraft landing on AEP after a flight from Iguaz£ Falls, skidded off the runway with eleven people on board (2 crew, 9 passengers). No fatalities or injuries. Heavy rain reported over Buenos Aires at the moment of the incident. The Learjet stopped after skkiding on the grass. AEP single runway 18/31 was closed for about 4 hours after this incident till the aircraft was removed. As a consecuence of this, a great air congestion was formed and at least 20 commercial flights were diverted to others airports (FDO, EZE, MVD) 3.2 Cause In a general aviation flight, during the landing run phase, loss of directional control of the aircraft, runway exit, collision with beacons and signs in the maneuvering area, ending with the landing gear half-buried on the left strip; due to probable runway hydroplaning condition. Contributing factors 1) Landing operation in storm weather conditions with heavy rain and cross wind. 2) Abundant amount of water momentarily falling on the AD, probably excessive for the limitations of the aircraft type and the normal drainage capacity of the runway. 3) Inadequate runway friction coefficient, in touch zone; contributing to the probable hydroplaning condition and ineffective braking of the aircraft. 4) Non-compliance with applicable Aviation Standards – Lack of publication of the information “Slippery slope in wet conditions”. 5. Inadequate implementation of the Operational Safety Management System (SMS).