Ralph Ambrose O'Neill (December 7, 1896 – October 23, 1980) was a Mexican flying ace from World War I credited with 103 combat patrols and five aerial victories. He was the first "Chief" Commander of the modern Mexican Air Force. He was also a pioneer of commercial aviation.

Rafael Ambrose O'Neill was born in Durango, Durango, Mexico on 17 December 1896 to father Ralph Lawrence O'Neill, an Irish Catholic candidate for Senator in Arizona; and to a Mexican mother, Dolores (Avila) O'Neill, of Castilian lineage. He was raised in the United States and began a career in the mining industry where his father operated the newspaper for the border town of Nogales, Arizona. O'Neill entered the United States Air Service in August 1917. In March 1918, he was assigned to the 147th Aero Squadron, flying the Nieuport 28 and the SPAD S.XIII. From 2 July to 31 October 1918, teaming with such squadron mates as Kenneth Porter, James Meissner, Francis Simonds, and James Healy, he shot down five German airplanes. He was awarded a total of three of the army's highest honor, the Distinguished Service Cross with two Oak Leaf Clusters along with the Distinguished Flying Cross (United States) and the French Croix de Guerre with palm. O'Neill claimed to have made an additional six unconfirmed victories for a total of eleven. He was the winner of the Tilton prize for becoming one of the first five American aviation aces of World War I.

A real character amongst his squadron, O'Neill was given the nickname "The Snake" for his unorthodox flying techniques, and fierce aggression in seemingly unfavorable odds. He was amongst the first combat pilots to paint the now-infamous "Sharks Teeth" Nose art in order to strike fear into the enemy. After gaining notoriety, he was also said to go into battle sitting on a large frying pan, which subsequently saved his life from machine gunfire.[1]

After the war, with his fluency in Spanish, O'Neill was hired to be the South American representative for Boeing and the Pratt & Whitney Aircraft Company, affording him introductions to many heads of state.

In August 1920, he signed a five-year contract to build a functional Mexican Air Force and train Mexican pilots, as Mexico was undergoing numerous violent ideological uprisings and military coups following the Plan of Agua Prieta. On September 9, he was made Chief of the Department of Aviation of the Mexican Army. In anticipation of O'Neill's arrival, French Farman F.50 twin-engine night bombers were purchased. According to the Secretary of War, in August 1920 the entire inventory consisted of only 13 aircraft. Nine were ill-equipped, mixed and matched engine, nationally-constructed biplanes. These were broadly considered still to be prototypes not suitable for concerted battle. Four more were monoplane scouts, five other planes were in repair and the rest at the TNCA were considered antiquated, wrecked, or beyond repair. The branch consisted of 27 pilots, only 4 possessing over 40 hours of flight time, and 17 of which were new cadets. With the current arsenal underwhelming and obsolete, O'Neill began to acquire air-cooled engines and new aircraft such as French Morane-Saulnier and 35 British Avro 504 model K and J for the flight school. These would later be copied and produced in Mexico under the name Avro Anáhuac.

"Jefe Rodolfo" as he was then known, would present himself to manufacturers and foreign leaders under made-up titles such as "Major-General" in order to garner prominence and legitimacy. He was the first to introduce the term "Fuerza Aérea Mexicana" (FAM) naming the organization as such. The next step was the formation of classified fighter, bomber, observation and forward reconnaissance squadrons, as well as the decentralization of Air Force units throughout the country at strategic bases. Other than the infrastructure itself, O'Neill was responsible for the invention of tactics, standard procedures and other scenario protocols never before implemented. O'Neill then set to work with his co-instructors German Fritz Bieler and Frenchman Joe Ben Lievre, using the first intercom, basically a hose and funnel to communicate in an open cockpit, known as the "Gosport System", invented by Robert Smith-Barry.

In 1923, O'Neill flew several decisive combat missions against ex-president Adolfo de la Huerta who had started an armed rebellion with sitting president Álvaro Obregón(O'Brien). The irony being that De La Huerta had been the one who hired and first equipped O'Neill; De La Huerta was soon to be the architect of his own demise. Under O'Neill's command, the Mexican Air Force achieved victory against overwhelming odds, where some 60% of the original Mexican army had been enticed to turn against the sitting government. After securing 17 new De Havilland DH-4B aircraft from America, O'Neill's patriots easily out-maneuvered the insurgents. On January 29, 1924, at Esperanza station, the tide of the war changed in favor of the loyalists thanks to better-organized ground and air co-operation along with new formations of synchronized aerial strafing runs and relentless resupply. [2]. Many of the rebels had never encountered combat aircraft before and were left in utter dismay. During one such mission, O'Neill was able to single-handedly free a hi-jacked passenger train, as the rebels abandoned their posts. The loyalist forces eventually crushed the strongholds in Veracruz and Jalisco and De La Huerta Fled the country. O'Neill became the first to prove the resilience of air superiority on a truly grand scale. On December 19, 1924, O'Neill was promoted to the now official rank of Brigadier General, being amongst the youngest in history, at the age of 28.

A military dictatorship had clearly been averted, but this was not the end of the country's woes. Many influential political and military commanders were executed by Obregón after the failed coup. Since Obregón could not run for reelection, the power vacuum was filled by an anti-catholic regime. The new Mexican president Plutarco Elías Calles promoted the creation of the Mexican Catholic Apostolic Church, independent from Rome, which led to a civil war, known as the Cristero War killing 100,000. Soon, state control was exerted over all public broadcasts. In addition, Calles rejected the Bucareli Treaty, almost starting a war with America. In the ensuing turmoil, O'Neill left Mexico in December 1925 and returned to the United States Army Air Reserve where he was reinstated to the rank of Colonel (United States).