Gustave Delage became Nieuport’s chief designer in 1914 and moved the firm away from its pre-war racing monoplanes toward a series of small, agile biplane scouts. His signature idea was the sesquiplane — a lower wing far narrower than the upper, carried on V-shaped interplane struts.

O Nieuport 11 “Bébé” of 1915 proved the concept: it was one of the aircraft that broke the Fokker Scourge, and it became the direct ancestor of the more powerful Nieuport 17 and the whole Nieuport 16/17/23/24/27 line that followed.

A conventional biplane has two full wings braced together for strength. Delage’s sesquiplane replaced the lower wing with a narrow surface built around a single spar, joined to the upper wing by a single V-strut on each side. The pilot could see past it downward and forward; the aircraft was light and turned superbly.

The cost was torsional rigidity. With only one spar, the narrow lower wing could twist under load and, in a prolonged or high-speed dive, was known to flex or even fail — a weakness the whole Nieuport family shared until the sturdier two-spar SPAD arrived.

The Bébé predated any reliable French synchronising gear, so it carried a single Lewis gun above the upper wing, angled to fire over the spinning propeller arc. On some machines a sliding rail — the kind later formalised on the British Foster mounting — let the pilot pull the gun down to change its 47-round drum in flight.

As gun-synchronising gear matured through 1916, later Nieuports such as the 17 gained a synchronised Vickers firing through the propeller — but the Bébé itself kept its over-wing Lewis to the end of its front-line career.

This is the caveat any honest account of the Nieuport family must include. In a prolonged or high-speed dive, the single-spar lower wing could twist and, in the worst cases, shed its fabric or break up.

Pilots adapted by not holding steep dives, and later the Royal Flying Corps ordered the lower wings strengthened. The Germans admired the layout enough to copy it in the Albatros D.III — which then suffered similar lower-wing troubles — while the Allies eventually moved to the stronger two-spar SPAD.

The Bébé sat at the head of a family. A more powerful version with a 110 hp engine became the Nieuport 16 ve Nieuport 17; refinements produced the Nieuport 23, o 24 ve 27, each a little heavier, faster and better armed than the last — but all sharing the sesquiplane silhouette Delage drew for the Nieuport 11.

Production was not confined to France. In Italy, Nieuport-Macchi built the Bébé under licence in large numbers, and in Russia the Dux works assembled it too — so the little Nieuport served far beyond the Western Front.

Per-aircraft procurement prices for French 1916 scouts are not reliably recorded in any consistent form, and wartime accounting bears no relation to a modern price. The Bébé was, by the standards of the day, a cheap and simple aeroplane — wood, wire and fabric around a small rotary.

What can be said is what it costs to keep an airworthy reproduction flying today: operators typically report on the order of $1,500–3,500 an hour, driven mostly by the care a century-old rotary design demands.