RAF Intelligence praised its exceptional manoeuvrability, further noting that "the plane was immensely strong",[5] though it was technically outclassed by faster, more heavily armed monoplanes.

By 10 June 1940, the date when Italy entered the Second World War, roughly 300 of the type had been delivered, which defended metropolitan cities, and important military installations at first.

[9] This pragmatic observation turned out to be correct as not only would the CR.42 be built in greater numbers than any other Italian fighter of the war, it would also see action on every front in which the Regia Aeronautica fought upon.

[1] Key features of the fighter, which was designated as the CR.42, included its relatively clean aerodynamic exterior, a very strong structure, and a high level of maneuverability, a combination which had traditionally appealed to Italian pilots according to Cattaneo.

[10] The type had been ordered as just a single element of the larger R plan, under which Italy was to procure 3,000 new fighter aircraft, such as the monoplane Fiat G.50 and the Macchi C.200, to equip and expand its air services.

The CR.42bis and CR.42ter featured increased firepower, while the CR.42CN was a dedicated night fighter model, the CR.42AS was optimised for performing ground attack missions, and the CR.42B Biposto commonly served in a twin-seat trainer role.

Beginning in 1938, Fiat had worked on the I.CR.42, then gave the task to complete the project to CMASA factory in Marina di Pisa on the Tirreno sea coast.

During test flights, it demonstrated its ability to attain a top speed of 518 km/h (322 mph), as well as a maximum ceiling of 10,600 metres (34,777 ft) and a range of 1,250 kilometres (780 mi).

[10] The CR.42 was typically powered by a single supercharged Fiat A.74R1C.38 air-cooled radial engine which, via a gearing apparatus, drove a metal three-blade Fiat-Hamilton Standard 3D.41-1 propeller of 2.9 metres (9 ft 6 in) diameter.

'"[22] On 13 June 1940, three days after entry of Italy into the war, 23 pilots from 23° Gruppo of 3° Stormo escorted a flight of ten Fiat BR.20 bombers to bomb the French naval base of Toulon.

Later that day, they attacked French Air Force base of Hyères, in the Provence-Alpes-Côte d'Azur region in southeastern France, hitting approximately 50 enemy aircraft on the ground and destroying at least 20 of them.

Cattaneo speculated that the light losses experienced during the Battle of France had persuaded the Regia Aeronautica that the type was considerably more effective than it was against the modern frontline fighter aircraft that it would be coming up against, and thus had encouraged this brief deployment.

[30] In the present day, the RAF Museum at Hendon, London has a CR.42 on static display from this time; this aircraft had reportedly force-landed in Suffolk with a broken oil pipe, with the pilot surviving.

Flight Lieutenants Peter Keeble and Burges scrambled to intercept them, and the resulting action greatly impressed the Malta defenders with the CR.42's maneuvering capability.

Keeble tried to dogfight with the Italians, but his engine was hit and his Hurricane dived into the ground at Wied-il-Ghajn, near Fort Rinella, and blew up; he was the first pilot to be killed in action at Malta.

A suggestion was made that the Hurricane should put down a bit of flaps as this might enable it to turn with the CR.42, but the only realistic proposal was to climb above these aircraft to be in an advantageous position.

[37][14] According to Cattaneo, the CR.42 achieved a degree of success as a night fighter, proving itself to be effective against RAF bombers that were bombing industrial targets throughout northern Italy during 1942.

[14] In autumn 1940, Regia Aeronautica sent 18° Gruppo (of 56° Stormo) in Belgium with 83a, 85a and 95a Squadriglia equipped with CR.42s as part of the Corpo Aereo Italiano, an independent air corps for operations against Great Britain.

[48] Operations involving the CR.42 were typically hampered by wider logistical issues; the Royal Navy had prevented Italian supplies reaching East Africa and aerial transportation alone proved to be insufficient.

On 29 June, a group of CR.42s from 2° Stormo scrambled to intercept an inbound formation of Blenheims, estimated as totalling nine aircraft, that were in the process of bombing the airfield of Tobruk T2.

The 12.7 mm Breda-SAFAT could fire an effective explosive bullet, but the Gladiator's Brownings were able to shoot 2.5 more rounds per second than the synchronized Italian machine guns.

The Axis effort to reinforce the Iraqi insurgents was insufficient and the coup had quickly been put down; however, this contributed to the decision to invade Syria that resulted in a substantial diversion during an already critical moment for the Allies.

The Hungarians, while aware that the CR.42 was conceptually outdated in comparison to the newer generation of monoplanes, had considered the rapid re-equipment of their fighter component to be of vital importance.

They claimed six additional kills, losing a single aircraft on 12 July, when 2nd Lieutenant Gyõzõ Vámos collided in a dogfight with a Polikarpov I-16 and bailed out, surviving.

[73] On 11 August, Hungarian Fiats escorted six Caproni Ca.135s, commanded by Sen Lt Szakonyi, on their way to bomb a 2 km (6,560 ft) bridge across the Southern Bug River in the city of Nikolayev, on the Black Sea.

[67] After the German 11th Army captured Nikolayev on 16 August, the commander of Luftflotte 4, Col Gen Lohr, decorated the successful Hungarian crews at Sutyska.

[77] The exact quantity of CR.42s delivered to Belgium prior to the German attack on 10 May 1940 has been estimated by historians to fall between 24 and 27 aircraft, the last of which having been transported to France and lost in the railway station at Amiens.

[14] The Swedish Air Force purchased various types of Italian combat aircraft during 1939–1941, as an emergency measure enacted in response to the outbreak of the Second World War.

Between February 1940 and September 1941, Sweden received a total of 72 CR.42s; these fighters were equipped with radio sets, 20-millimetre (0.79 in) armour plate behind the pilot and ski landing gear for winter operations.

[86] Swedish pilots appreciated the J 11's formidable close-in dogfighting abilities;[87] however, they would often complain about the type's low speed, insufficient armament and the open cockpits that were unsuited for the severe climate of Scandinavia.