of six different versions of the Caravelle in production, designated III, VI-N, VI-R, 10A, 10B, and X-BIR. Of these, the Caravelle III was considered to be the basic version of the airliner, while the other variants featured an increasing number of improvements. The Caravelle VI-N was equipped with more powerful Avon 531 engines and an additional heat exchanger for the air conditioning, while the Caravelle VI-R, which had come about as a result of demands by U.S. carrier United Airlines, was furnished with thrust reverser-equipped Avon 352s, a revised windscreen design, soundproofing, a new luggage compartment door, and wing spoilers. The Caravelle 10A and 10B, which differed only in the engines used and were commonly referred to as the Super Caravelle, featured the improvements of the VI-R in addition to a high degree of further design changes. The more high-profile modifications included a stretch of the fuselage by ; a highly altered wing; an aerodynamic fairing behind the fin of the tailplane; expanded cargo capacity via raised floor support struts; and higher cabin windows. Other changes included the adoption of variable-displacement pumps for the hydraulic system and the use of AC-based generators in place of earlier DC counterparts along with an auxiliary power unit (APU). The redesigned wing was equipped with double-slotted Fowler flaps, additional and repositioned stall vanes, aerodynamic improvements to the wing root and adjustments to the leading edge that improved the performance of the wing during the crucial takeoff and landing phases of flight. Despite its commercial success, however, the Caravelle was soon displaced from being the focus of Sud Aviation's development efforts as the majority of the company's design engineers were progressively reallocated onto an entirely new project that was intended to produce a successor to the Caravelle. The project was relatively ambitious, having the aim of producing a viable supersonic transport that possessed the same general size and range as the Caravelle. It was decided that the envisioned supersonic airliner should be naturally named after the firm's recent success, thus the Super-Caravelle name was applied to the design. Ultimately, the work on the Super-Caravelle would be merged with similar work that had been undertaken by Britain's Bristol Aeroplane Company, and would result in the development of Concorde. In total, 282 Caravelles of all types were manufactured (2 prototypes or pre-production aircraft and 280 production aircraft); reportedly, Sud Aviation's projected break-even point for the type had