Question: The Curtis Fling School was started by Glenn Curtiss to compete against the flying school of what brothers who made the first controlled, sustained flight of a powered, heavier-than-air aircraft on December 17, 1903?

Context paragraphs:
Wright Flyer: The Wright Flyer (often retrospectively referred to as Flyer I or 1903 Flyer) was the first successful heavier-than-air powered aircraft.  It was designed and built by the Wright brothers.  They flew it four times on December 17, 1903, near Kill Devil Hills, about four miles south of Kitty Hawk, North Carolina, US.  Today, the airplane is exhibited in the National Air and Space Museum in Washington D.C. The U.S. Smithsonian Institution describes the aircraft as "the first powered, heavier-than-air machine to achieve controlled, sustained flight with a pilot aboard".  The flight of "Flyer I" marks the beginning of the "pioneer era" of aviation.

Voisin: Voisin was a French aircraft manufacturing company, one of the first in the world.  It was established in 1906 by Gabriel Voisin and his brother Charles, and was continued by Gabriel after Charles died in an automobile accident in 1912; the full official company name then became Société Anonyme des Aéroplanes G. Voisin (English: Aeroplanes Voisin public limited company ).  It created Europe's first manned, heavier-than-air powered aircraft capable of a sustained (1 km), circular, controlled flight, including take-off and landing, the Voisin-Farman I.  On 28 December 1909, French aviator M. Albert Kimmerling made the first manned, heavier-than-air powered flight in South Africa or even Africa in a Voisin 1907 biplane.

Curtiss Flying School: The Curtiss Flying School was started by Glenn Curtiss to compete against the Wright Flying School of the Wright brothers.  The first example was located in San Diego, California.

Question Mark (aircraft): Question Mark (""?"")  was a modified Atlantic-Fokker C-2A transport airplane of the United States Army Air Corps.  In 1929, commanded by Major Carl A. Spaatz, it was flown for a flight endurance record as part of an experiment with aerial refueling.  "Question Mark" established new world records in aviation for sustained flight (heavier-than-air), refueled flight, sustained flight (lighter-than-air), and distance between January 1 and January 7, 1929, in a non-stop flight of more than 150 hours near Los Angeles, California.

Curtiss NC-4: The NC-4 was a Curtiss NC flying boat which was designed by Glenn Curtiss and his team, and manufactured by Curtiss Aeroplane and Motor Company.  In May 1919, the NC-4 became the first aircraft to fly across the Atlantic Ocean, starting in New York State and making the crossing as far as Lisbon, Portugal, in 19 days.  This included time for stops of numerous repairs and for crewmen's rest, with stops along the way in Massachusetts, Nova Scotia (on the mainland), Newfoundland, and twice in the Azores Islands.  Then its flight from the Azores to Lisbon completed the first transatlantic flight between North America and Europe, and two more flights from Lisbon to northwestern Spain to Plymouth, England, completed the first flight between North America and Great Britain.

Curtiss B-8: The Curtiss B-8 was an early air-cooled 8-cylinder engine used for a number of aircraft and one motorcycle designed by Glenn Curtiss.  It powered the AEA June Bug in 1908, becoming the first Curtiss engine to power a heavier-than-air aircraft in sustained flight.

Wright brothers patent war: The Wright brothers patent war centers on the patent they received for their method of an airplane's flight control.  The Wright brothers were two Americans who are widely credited with inventing and building the world's first flyable airplane and making the first controlled, powered and sustained heavier-than-air human flight on December 17, 1903.

History by Contract: History by Contract is a book by early aviation researchers Major William J. O'Dwyer, U.S. Air Force Reserve (ret.)  and Stella Randolph about aviation pioneer Gustave Whitehead.  The book focuses on an agreement between the Smithsonian Institution and the estate of Orville Wright, which stipulates that the Smithsonian, as a condition of owning and displaying the 1903 Wright Flyer, must recognize and label it as the first heavier-than-air machine to make a manned, powered, controlled and sustained flight.

Wright brothers: The Wright brothers, Orville (August 19, 1871 – January 30, 1948) and Wilbur (April 16, 1867 – May 30, 1912), were two American brothers, inventors, and aviation pioneers who are generally credited with inventing, building, and flying the world's first successful airplane.  They made the first controlled, sustained flight of a powered, heavier-than-air aircraft on December 17, 1903, four miles south of Kitty Hawk, North Carolina.  In 1904–05 the brothers developed their flying machine into the first practical fixed-wing aircraft.  Although not the first to build and fly experimental aircraft, the Wright brothers were the first to invent aircraft controls that made fixed-wing powered flight possible.

Boeing School of Aeronautics: The Boeing School of Aeronautics was started by Boeing to compete against the Wright brothers' Wright Flying School and Curtiss Flying School in San Diego, California.  Founded in 1929 at Oakland Municipal airport, the school started with a staff of 19 and 100 students.  It was licensed by the Aeronautical Chamber of Commerce, who had taken over the licensing of aviation schools.

Supporting paragraphs: Curtiss Flying School Wright brothers
Answer: The Wright brothers