The Heinkel He 274 was a German heavy bomber aircraft with pressurized crew accommodation developed during World War II, designed for high-altitude bombing.

[2] Heinkel had foreseen that an individually engined version of his bomber would someday be preferred, quite unlike the requested fitment of the coupled pairs of Daimler-Benz DB 601 inverted V12 engines, each known as a DB 606 — weighing some 1.5 tonnes apiece — which ended up being fitted to all of the eight He 177 V-series prototypes at the request of the RLM, and the Luftwaffe High Command, with the concerned government agencies citing the desire for a dive-bombing capability to be present even with a heavy-bomber-sized offensive warplane, something Ernst Heinkel vehemently disagreed with.

The defensive armament had been reduced to a trio of Ferngesteuert-Lafette FL 81Z remote gun turrets, each with a twin-barrel MG 81 armament installation each in an upper nose mount, forward dorsal and (as part of the Bola casemate-style gondola under the nose) forward ventral location each, and a single MG 131 machine gun in an He 177A-1-style, pressurized manned flexible tailgun emplacement.

[citation needed] By October 1941, a more developed "He 177H" specification for a high-altitude Heinkel-designed heavy bomber[6] had emerged from the proposed A-2 and A-4 coupled-engine designs, with the intent of carrying a 2,000 kg (4,410 lb) bombload over a maximum range of some 3,000 km (1,895 mi), and accepted by the RLM for the first time since the rejection of Dr. Heinkel's initial November 1938 request for two of the early He 177 V-series prototype airframes to get them, an individual four-engine installation was being considered for any He 177-based bomber airframe, with a quartet of either BMW 801 or DB 603 unitized-installation engines — the DB 603 powerplants being unitized in a Heinkel factory-specific design also used for the He 219 — among the choices of powerplants being specified, with the same sort of reduced-armament defensive weapon format as the A-2 and A-4 were intended to have.

[7] A pair of the early He 177A-0 pre-production prototypes were renamed the He 177 V10 and V11 for the purposes of high-altitude trials and were to be the first to test the A-4 pattern pressurized cockpit design at altitude.

This resulted in a trio of parallel programs under development by the Heinkel engineering shops for four-engined heavy bomber designs, from February 1943 to 20 April 1944.

[14] Major differences between the He 274 and the He 177 A were abandonment of the twin coupled "power system" engine arrangement in favor of four independent DB 603A-2 fully unitized engines, cooled by annular radiators nearly identical in appearance to those on the similarly-powered Heinkel He 219 night fighter as an integral part of each "unitized" engine's installation, an extended rear fuselage with a twin tail fin empennage, a pressurized double glazed cockpit of nearly identical external appearance to the 177A's standard "Cabin 3" nose, a longer wingspan, and a more conventional, single oleo strut-per-side set of twinned-wheel main undercarriage, abandoning the cumbersome four-strut main gear system of the He 177A, needed for the earlier design's pair of larger-diameter, four-blade propellers.

[citation needed] The He 274's advanced, high-altitude cockpit, despite its external resemblance to that of the He 177A, comprised a pressurized compartment for a crew of four employing double walls of heavy-gauge alloy, hollow sandwich-type glazing and inflatable rubber seals.

The He 274 V1 was being readied for flight testing at Suresnes in July 1944 when the approach of Allied forces necessitated the evacuation of Heinkel personnel working on the project.

Minor difficulties had delayed the flight testing and transfer of the aircraft to Germany, and orders were therefore given to destroy the virtually completed prototype.