Dornier constructed a number of aircraft that were later to be dubbed the "Flying Pencils" due mainly to the long thin outline of the fuselage. probably the most famous, and the one that was to take part in the Battle of Britain period was the Dornier 17. Because of the fuselage shape, it was highly improbable that the aircraft was originally designed as a passenger aircraft for the Lufthansa Airline. More than likely the designers hoped that it would be accepted as a transport although many believe that the aircraft was destined to become a mailplane that could also carry four to six passengers. The first flight of the Dornier was on November 23rd 1934, and was rejected by Lufthansa and the prototypes were left in a hangar, only to be discovered a few years later by Robert Untucht who was the air ministry liaison officer, and a test pilot with Lufthansa. he tested the Dornier, and believed that with modifications, the aircraft would more than handle the role of a bomber in the military arena. The original Do17 had a pair of 750 hp BMW engines that propelled the aircraft at 225 mph, but after Robert Untucht made the first modifications and by the time the Do17 had reached version 4, the BMW engines were retained, but the tailplane section had been redesigned doing away with the single tailfin, and replacing it with double tailfins and rudders. In an effort to increase speed even further, the version 5, designated Do17Z V5 was equipped with Hispano engines, and although heavier it managed to give the Dornier a top speed of 245 mph, which at the time, was far greater than any fighter, and this was proven in 1937 when the Do17 saw service in Spain, and outpaced all of the Republican fighter aircraft. Modifications continued, the Do17Z V8 was tied with the Daimler Benz DB 600A engines that were producing 1,000 horsepower. , the Do17E was the first production bomber to see service with the Luftwaffe and the designers reverted back to the 750 hp BMW V1 engines at the sacrifice of a lower top speed. The Do17M was equipped with 1,000 hp Bramo 323A engines, but otherwise stayed the same as the Do17E. With more powerful engines coming out of a number of factories in Germany, the Do17K of which a number were bought by Yugoslovia were powered by Gnome-Rh?14N engines and were amongst the fastest of the Dorniers by attaining a top speed of 259 mph. The Spanish Civil War was to be the toughest test yet on the Do17 bomber. It proved to be fast, in fact was fast enough to outpace any enemy fighter, although it could not match Germany's own Bf109, but one important lesson was learnt. It was vulnerable to enemy gunfire, especially in the forward section. The nose had been shortened on the Do17E and the Do17F variants, but the firing arc of the forward gunner was restricted somewhat and the narrow diameter of the fuselage of the Do17 which was how it became known as the "Flying Pencil" meant cramped conditions for the cockpit area of the aircraft | 
