The DORNIER Do 17 twin engined bombers were used by the Luftwaffe more than any other type for the numerous photographic reconnaissance flights over France and over Great Britain during the early days of the war. The Do 17 was one of the first modern types to go into production for the Luftwaffe in 1935. Since then it has been fitted with three different types of motor. The prototype Do 17 flew with 660 h.p. B.M.W. VI un-supercharged liquid cooled upright Vee motors in the Summer of 1936. It had a top speed of 400 km.h. (249 mph.) at sea level. Later the 880 h.p, B.M.W. cylinder supercharged air-cooled radials were installed. They raised the top speed to 445 km.h. (276 m.p.h.) at 3,000 m. (9,840 ft.).

Later Do 17s were built with 1,050 h.p. Daimler Benz DB.600G motors. With them the top speed went up to 470 km.h. (292 m.p.h.) at 14,800 ft.  The Do 17 and later Do 215/217 aircraft were all-metal high wing cantilever monoplanes .  They had twin fins and rudders at the ends of the cantilever tail plane just outboard of the centre-lines of the engines.

 
The original long tapered nose gained the Do 17 the name of the "Flying Pencil." It was flush riveted to further enhance its speed. The wings were without dihedral and tapered towards the tip. The fully monocoque fuselage had an aluminum stressed skin covering. The full cantilever tail plane is set at a small dihedral angle. Trim tabs are used on all the movable control surfaces. The elevators are mass balanced with external balances, which passed through slots in the tail plane. The twin rudders had aerodynamic as well as mass balances. The fixed surfaces have metal covering, the movable surfaces fabric.

The undercarriage is retracted hydraulically. The wheels, mounted between two oleo legs and equipped with mudguards and brakes, were raised backwards in to the motor nacelles and enclosed by hinged doors, so that only the tire was left protruding. This feature prevented many a 'wheels up' landing from doing a great deal of damage to the underside of the plane. While not all types had a retractable tail wheel, on those that did, the tail wheel retracted vertically in to the fuselage.

The Do 17 carried a crew of three, all in front of the wing. The pilot sat on the port side of the fuselage, so that there was room for the bomb-aimer to pass to his prone position below. A navigation compartment with hinged chart table occupied the space between the back of the pilot and the front spar of the wing.

Forward armament consisted of two fixed machine guns in the front cowling, operated by the pilot. The bombs are stowed horizontally in the centre section of the fuselage between the spars. Up to 1,000 kg. (2,205 lb.) can be carried internally. The Do 215 was built on the same jigs as the Do 17 and only varied from it in minor detail.

They were robust enough to endure terrible amounts of gunfire, especially small calibre gunfire. Their strength did not depend upon bracing wires and wooden spars: these metal bombers had armour protection, with some of the vital mechanical parts duplicated. Even more valuable were the self sealing fuel tanks.

First combat was in Spain with the Legion Condor where the type was quite successful against an ever-diminishing enemy air force and their Soviet I-15/I-16 fighters. They were also quite successful in the opening year of the war in Europe, but when faced against a determined enemy were not as immune as the crews would have wished. By mid-war, the Do-17 was out of active service on most fronts with the later 215 and 217 operating in small numbers and mostly at night.