In September 1917, the 2nd lieutenant Gheorghe Jienescu was selected and sent in England, at Oxford, for training and specialization at the Technical and Flight School, then in France, at Miramas and Pau, for specialization as fighter pilot. On 1 September 1919 he received the pilot license no. 164.

Between 1923 and 1926 he was the director of Flight School of Tecuci, where he trained four classes of fighter pilots, the first in the Romanian aviation. In the same period he edited the first important flight regulation manual of Romanian aviation.

In 1928 he graduated the Superior School of War of Bucharest, in the rank of major. He became the second aviation officer, after Major Achile Diculescu, to graduate this institution, receiving the license of air force staff officer. He was appointed, for a short period of time, staff officer at the Air force Inspectorate, the Training Bureau, then chief of staff at the Air Division.

In 1934 Gheorghe Jienescu was appointed commander of the Air Fighting Fleet of fighters and bombers at Pipera.

In 1935 he directed the Bucharest – Capetown flight, started on 14 April with three “Icar Universal” aircraft, a renowned event around the world and regarded as the most important flight of the Romanian military aviation.

In 1940, Colonel Aviator Gheorghe Jienescu was appointed chief of staff of the newly established Air Force Headquarters, commanded by General Constantin Celareanu. On 14 September 1940 he was appointed, by General Ion Antonescu, undersecretary of state at the Department of Defense for Air and Navy.

Between 27 January 1941 and 23 August 1944, Colonel Aviator Gheorghe Jienescu, later General of Air Squad Aviator, was minister secretary of state at the head of the State Undersecretariat of Air, organism created in October 1940 to coordinate the activity of Romanian Royal Aeronautics.

On 22 June 1941, the day of the beginning of military operations against the Soviet Union, General Gheorghe Jienescu transmitted the following order to the air force: “Flying personnel, the honor of carrying to victory, on the sky of Romanian people, the tricolor cockade, belongs to you. The order of the day is: the crew that runs out of ammunition and in the clash does not see victory, is crashing with the plane in the enemy bird. Young airmen: the entire country is expecting the supreme sacrifice from you; the day has come for great deeds; make our actions worthy of legend. You did it at peace, I am confidant you will also do it without hesitation at war, to be worthy of the trust the King, the Leader and the Motherland always had in you. Young airmen: the horns are calling and the woods are resounding, the sky is rumbling; in the sound of engines, the song of nation, to arms, to control sticks, with God forward!”

In the period Jienescu made part of the Antonescu government, he promoted the doctrine of the offensive role of air force and the simple and flexible organization for all air branches. “With ten bomber crews (one squadron) it is obtained a firepower equivalent with 13 tons of explosive, in a short period of time, while an artillery battery requires 24 hours to project the same quantity.” – Gheorghe Jienescu. “The aeronautics claims a classification superior to the other branches of the Army. This superiority is required both numerical but, foremost, qualitative.”

On 14 November 1941, he was decorated with the Order of “Michael the Brave” 3rd class, through the Royal Decree 3202.

The events of 23 August 1944 broke off the career of General Aviator Gheorghe Jienescu, on 24 August being fired from the position of minister of Air. In the period September 1944 – February 1946, Gheorghe Jienescu was confined at his residence, being guarded by paratroopers.

From February 1946 until February 1948 he was arrested and locked up in the prison of the Military Headquarters of the Capital. He was put on trial in the batch of Antonescu government and, by the sentence no. 27 of 6 February 1948 of the Superior Court of Justice Bucharest, he was sentenced to 20 years of prison, civic degradation and the seizing of his estate, being charged with “crime for disaster of the country” according to the Law 312/1944.

He was pardoned and released in April 1964, on the basis of the Decree of State’s Council no. 176/1964. Out of the 17 years of severe imprisonment, 7 were in complete isolation. At the date of release, Gheorghe Jienescu was seventy. According to the stipulations of the Decree no. 2993/1959 of the Presidium of the Great National Gathering, he was not entitled to pension. He died on 3 April 1971 due to a heart attack, at the age of 77.