Original sentence: After WWII the Air Force underwent several developmental stages, the first major air force modernization being performed from 1953 to 1959.At the beginning of 60-ies supersonic fighters were introduced, followed by intensive growth of serbian aviation industry in that period.During the April war in 1941, in 9 war days, 145 pilots died in air combats, while 576 members of the Air Force perished on ground.The pilots soon applied the experience gained in the Balkan wars to the WWI battles, thus becoming a worthy opponent to the stronger enemy forces.This day was by the Act of king Aleksandar I Kardjordjevic proclaimed the Air Defense Artillery Division’s day
Edited sentence: After WWII our Air Force underwent several developmental stages, the first major air force modernization being performed from 1953 to 1959.At the beginning of 60-ies supersonic fighters were introduced, followed by intensive growth of our aviation industry in that period.During the April war in 1941, in 9 war days, 145 pilots died heroically in air combats, while 576 members of the Air Force perished on ground.Our pilots soon applied the experience gained in the Balkan wars to the WWI battles, thus becoming a worthy opponent to the stronger enemy forces.This heroic deed was performed by the famous gunner Radivoje-Rade Ljutovac, and this day was by the Act of king Aleksandar I Kardjordjevic proclaimed the Air Defense Artillery Division’s day