On 19 December 1914, Arnoux was inducted for military service with the 2e Groupe d'Aviation. He was stationed on the Serbian front as a driver until February 1916. After being decorated by the Serbs, he was returned to France for pilot's training. On 23 May 1916, he was granted Military Pilot's Brevet No. 3539. After some further flying experience, he was trained on Nieuport fighters. On 13 April 1917, he was assigned to a Nieuport squadron, Escadrille 49. He shared a victory with a squadron-mate on 28 June 1917. During the latter part of 1918, he would share two victories over enemy aircraft; he would also single-handedly destroy two German observation balloons.
Civilian flying career
Arnoux took part in many air races and events during the 1930s. In August 1931 he took part in the Dunlop Cup Tour of France, flying a Farman 234, and came second, winning 12,000 francs. The following year he entered the same aircraft in the Challenge International de Tourisme. In the Technical Tests, held at Staaken, Berlin, his aircraft managed only 39th place out of 41, and in the subsequent race around Europe, a distance of approximately over six days, he came 23rd out of 24 to complete the race. On 2 June 1933 he competed in the first Douze Heures d'Angers race, a competition confined to tourist two-seater aircraft with engines no larger than 8 litres. Flown around triangular course based at the Avrille Aerodrome at Angers, the race was to cover the furthest distance in twelve hours, combining endurance with speed. Arnoux flew a Farman 356 fitted with a Renault Bengali engine, covering at an average speed of, and coming in 6th place. In May 1934 Arnoux won the Coupe Deutsch de la Meurthe, flying a Caudron low-wing cantilever monoplane, fitted with a 300 hp Renault six-cylinder engine. The race was flown from Étampes-Mondésir Aerodrome over a triangular course, and Arnoux completed it 5 hours 8 minutes and 31 seconds, at an average speed of. Soon afterwards, in June, he made a presentation flight in his winning aircraft at an Anglo-French event at Buc Aerodrome to celebrate the 25th anniversary of Louis Blériot's 1909 flight across the English channel, which was attended by Blériot himself, President Albert Lebrun, the French Air Minister General Victor Denain, British Air Minister Lord Londonderry and Air Vice-MarshalPhilip Joubert de la Ferté. The following year however, he only managed third place. In July 1935 he won the third Douze Heures d'Angers, flying in twelve hours at an average speed of in a Caudron C.430 Rafale. In August 1935, flying a Caudron monoplane with a Renault engine, he set a new speed record for carrying a passenger. His speed was approximately. In mid-July 1936 he won the Douze Heures d'Angers for the second time, completing at an average speed of, in a race cut short by bad weather. Soon after, on 25 and 26 July 1936, he competed in the third annual Grand Prix of the Aero Club of France, in which aircraft flew from Deauville to Cannes the first day, and returning the next. Arnoux won in his Caudron C.684, with an average speed of, winning the cup and cash prize of 20,000 francs. In September he claimed a new world record for aircraft weighing not more than, flying over, at a speed of, and in October was the co-pilot of a Caudron C.448 Goéland, one of three aircraft taking part in a French Aero Club race from Paris to Saigon and back, a distance of, for a 1,800,000 franc prize. With his co-pilot :fr:André Japy|André Japy, he was in the lead, until an undercarriage failure at Karachi forced them to retire with a damaged wing. In August 1937 he took part on the Istres–Damascus–Paris Air Race, flying as co-pilot with Paul Codos in the Breguet 470Fulgur, and coming fifth in a race dominated by Italian Savoia-Marchetti aircraft. On 28 December 1937, flying a Caudron-Renault aircraft Arnoux set a new altitude record for a light single-seater, reaching a height of, and later established a new speed record, flying at an average speed of.
Military honors
Besides the Croix de guerre with six palmes and two stars, Maurice Arnoux also won two major French awards for valor: Médaille Militaire "Elite pilot who distinguishes himself each day by new exploits. Always prepared to accomplish all his missions with the same zeal and courage; pursuit, reconnaissance or strafing trenches. He has already downed two balloons and one aircraft and has executed missions successfully both in day and night reconnaissances of long distances without allowing himself to be impeded by enemy attacks. During the night of 17 September 1918, while on reconnaissance behind enemy lines to strafe a train station a low altitudes, he returned with his plane damaged by enemy fire. Five citations." Médaille Militaire citation, 4 October 1918 Chevalier de la Légion d'Honneur "Remarkable officer pilot as shown by his brilliant professional qualities and by his spirit, courage and ardor beyond praise. Always volunteers for the most painful and perilous missions. After having brilliantly served in an Escadrille of reconnaissance, he transferred to pursuit aviation where he was classed among the best. Has downed five enemy planes. Cited in orders eight times." Chevalier de la Légion d'Honneur citation, 13 July 1919
