The first Ford vehicle to have the bold new "aero" look styling was the 1981 Ford Probe III concept car. The good reception this received encouraged Ford management to go ahead with a production car with styling almost as challenging. This "aero" look influenced Fords worldwide; the 1983 Ford Thunderbird in North America introduced similar rounded, flowing lines, and some other new Fords of the time adopted the look. The aerodynamic features of the Sierra were developed from those first seen in the Escort Mark III — the "Aeroback" bootlid stump was proved to reduce the drag coefficient of the bodyshell significantly, which was a class leading 0.34 at its launch .
The aerodynamic styling of the Sierra would later be seen in North America's equally revolutionary Ford Taurus.
At first, many found the design blob-like and difficult to accept after being used to the sharp-edged, straight-line styling of the Cortina, and it picked up nicknames such as "Jellymould" and "The Salesman's Spaceship" (the latter thanks to its status as a popular fleet car in the United Kingdom). Sales were slow at first. It was later in the Sierra's life that the styling began to pay off; ten years after its introduction, the Sierra's styling was not nearly as outdated as its contemporaries, even though all major competitiors were newer designs, although the Sierra had been tweaked on several occasions. The most notable changes came at the start of 1987, with a major facelift the addition of a Sapphire saloon. As other manufacturers adopted similar aerodynamic styling, the Sierra looked more normal.
The revolutionary design and new name of the Cortina replacement attracted notable criticism on television from comedian Alexi Sayle, who blasted the Sierra for "not speaking English volumes" the way the Cortina had.
Early versions suffered from crosswind stability problems, which were addressed in 1985 with the addition of "strakes" (small spoilers), on the rear edge of the rubber seals of the rear most side windows. These shortcomings saw a lot of press attention, and contributed to early slow sales. Other rumours that the car hid major crash damage (in part true, as the new bumper design sprung back after minor impact and couldn't be "read" to interpret major damage) also harmed the car's reputation. This reached near-hysterical heights at one point with UK press making a report that Ford would reintroduce the previous Cortina model out of desperation. However, these reports were swiftly denied by Ford's overheads.