In September 11th 2001 was attack on New York and in March 11th 2004 was attack on Madrid. As an expression of solidarity with the American and Spain people, Europe has declared 14 September and 15 March a days of mourning, respectively. During the three minute-silence period experimental tests were carried in Croatian National Dispatching Centre. Results indicated that the load, in the first case decreased about 2030 MW with frequency increased 113 mHz. In the second case frequency increased 83 mHz and load decreased about 1500 MW. The evaluation of the performed measurements showed control behavior of the European power system.