As World War 2 (1939-1945) progressed, German fortunes in the war took a turn for the worse during 1943-1944. The Allied bombing campaign proved one of the major factors in Germany beginning to switch its approach to a defensive-minded war in the air - one centered on fighters and interceptors armed with cannons and rockets. This led to a bevy of designs intended to meet the growing threat and stave off elimination and, while the turbojet was clearly the path to the future, the piston-engined fighter was here to stay for at least a while longer, the type having yet to reach its pinnacle.
As such, there was thought given to a "bridge" fighter design of sorts, that is, an existing airframe that could rather conveniently be converted to a jet-powered form by relatively simple installation of a turbojet in place of the piston engine. This led to a series of design studies from the usual German defense players, namely Focke-Wulf (makers of the war-winning Fw 190) and Messerschmitt (developers of the classic Bf 109) centered around this concept. For Focke-Wulf, this focused on the Fw 190 and, for Messerschmitt, this led to the Bf 109.
The eventual goal, beyond developing a tide-turning, high-performance fighter, was to create a single-seat, jet-powered platform utilizing as many existing components of in-service aircraft as possible. This would help to lower costs and shorten development times, ushering the new fighter into service perhaps within months. As the Bf 109 was available in quantity from German factories, the airframe was an excellent candidate for such a procedure - all this while the complex jet-powered Messerschmitt Me 262 "Schwalbe" was still in-development (it would be formally introduced in April of 1944).
The result of this study by Messerschmitt was an aircraft that was to retain the middle-aft fuselage section, tail, and cockpit of the Bf 109 - leaving the nose, some of the undercarriage, and the wing mainplanes to still be developed. The "tail-dragger" undercarriage of the original was replaced by a tricycle form in which the nose leg was borrowed from a left-over Me 309 prototype fighter (four prototypes were completed, the project ended in 1943) but the main legs were to be scratch-developed/built. Beyond this, engineers were forced to fabricate all-new wing mainplanes for the speeds expected from turbojet flight as well as an all-new lengthened nose assembly to house the intended cannon armament. The turbojet engines would be underslung at each wing member (as in the Me 262) giving excellent access for ground crews and keeping the fuselage clear for armament, avionics, and fuel stores.
Engineers soon found it difficult to procure parts from existing assembly lines simply due to wartime demand.
The cockpit, seating one, was heavily framed in the usual Bf 109 way and seated at the absolute center of the fighter. This presented issues with pilot vision for the long nose, low-mounted wings (with their underslung engine pods) as well as the raised fuselage spine aft of the cockpit all restricted critical views during ground-running and in-air action. The tricycle undercarriage was all-retractable with the nose leg folding back under the nose and the main legs pulling inwards towards fuselage centerline. All of the armament was to be concentrated at the nose (as in the Me 262) and centered on a battery of 4 x 30mm MK108 automatic cannons (as in the Me 262) or a mixed assortment involving 1 x 20mm MG151 automatic cannon with 2 x 30mm MK108 automatic cannons - the idea being that this weapons "pack" could be replaced as-needed based on supply-and-demand.
All told, the fighter had a running length of 30.1 feet, a wingspan of 42.6 feet, and a height of 8.5 feet. Loaded weight would reach 10,500lb. Power was to come from 2 x Junkers Jumo 004B-1 air-breathing turbojet engines developing 1,985lb of dry thrust each.
As this jet-powered Bf 109 form was never constructed, no performance specifications were realized (numbers on this page as estimates on the part of the author, based in the Me 262). It appears that there proved too many technical- and cost-related issues to "simply convert" and existing piston-powered fighter form to that of turbojet power and thus the various design ideas of the wartime period centered around this thinking eventually fell to history.