The SS 1 is a product of actually the Swallow Coachbuilding Company and is a 2-door sports saloon car. Produced for 5 years between 1931-1936, this model acquired the name Jaguar as another firm called the Walmsley Lyons and Co purchased the company and renamed the firm and the brand. 

Now, why this model was called Airline is because of the then Art Deco movement of the 1930s, when designers caught the imagination of aeroplane designs and tried to incorporate aircraft elements into their work. This meant the use of inclined door pillars, pillar-less side windows, down-slept lines, etc.