After a competitive 1990 season with 6 wins and which saw Prost loosing the title for 7 points, 1991 was going to be a disaster with no win for french duo Prost/Alesi. The team began the season with the 642, said to be an improvement of 641 type with aero, monocoque and suspensions modifications under the direction of S.Nichols. The 642, which gave satisfaction during winter tests, will be later said to be worse than the 641, with aerodynamic instability and bad suspension geometry. The 643 type, introduced at french GP, with aero input of J.C.Migeot, back to Ferrari in 1991, had to cure these problems. It will be a definitive improvement but couldn't change the basic design. On the engine side, the situation was not better, Ferrari continually improved them with 6 new specifications during the season (from type 291.1 to 291.6) but they seemed to be short on reliabilty, torque and also power. A poor year for the Scuderia, ending with the dismissal of Prost before the end of the season, they will have to wait 1994 to win again.