The F-104D (Lockheed Model 383-04-06) was the two-seat combat trainer version of the F-104C. It bore the same relationship to the F-104C as the F-104B did to the F-104A.
The D model was quite similar to the F-104B, but with the refinements of the F-104C. Like the F-104B, it had the large-area vertical fin with the extensive overhang behind the tailpipe. In order to make room for the second crewman, the nosewheel once again had to be made to retract rearwards, and the 20-mm rotary cannon of the F-104C had to be removed, limiting the air-to-air armament to a pair of wingtip-mounted AIM-9B Sidewinders (although provisions were later made for the mounting of another pair of Sidewinders underneath the fuselage). The provision for two underwing and two wingtip drop tanks was retained, boosting total fuel capacity by 730 US gallons. The AN/ASG-14T-2 fire control system of the F-104C was retained. The provision for the removable port-mounted in-flight refuelling probe of the F-104C was also retained.
The most visible external difference between the F-104D and the F-104B was the presence on the D of a cockpit canopy with a revised framing structure, with the two individual port-opening cockpit canopies being separated from each other by a fixed transparent area.
Provisions were made for the possibility of removing the rear seat of the F-104D, fitting the 20-mm rotary cannon, and flying the aircraft as a single-seater if the need should ever arise. However, I don't know if this was ever done in practice.
The performance of the F-104D was almost identical to that of the F-104C, but the reduced internal fuel capacity reduced its effective range considerably.
The F-104D was the last version of the Starfighter to built for the USAF. 21 F-104Ds were delivered between November 1958 and August 1959. They all went to the four squadrons of the 479th Tactical Fighter Wing that had already been equipped with F-104Cs. A further 83 F-104Ds ordered under FY 1957 funding were later cancelled when the USAF terminated all its Starfighter procurement plans.
Along with the F-104C, ADC F-104Ds were transferred to the Puerto Rico Air National Guard in 1967. The ANG operated these F-104C and D Starfighters until July 1975, when they were replaced by LTV A-7Ds. Most of the F-104Ds joined their single-seat F-104C cousins in the boneyards at Davis Monthan AFB, although six were transferred to Taiwan. At least 8 are now on display in various museums.
57-1314/1320 Lockheed F-104D-5-LO Starfighter c/n 483-5026/5032 1314 at Castle AFB, California with F-104B glass cockpit and marked as F-104B 57-1312. 1315,1316,1318,1319 sold to Taiwan 1319 at USAF History and Traditions Museum, Lackland AFB, Texas. 1320 at Travis AFB Museum, CA. 57-1321/1328 Lockheed F-104D-10-LO Starfighter c/n 483-5033/5040 1321,1326 sold to Taiwan 1322 at Grissom AFB, IN. 1323 at Pima Air Museum, Tucson, AZ. 57-1329/1334 Lockheed F-104D-15-LO Starfighter c/n 483-5041/5046 1331 at USAF Armament Museum, Eglin AFB, FL 1333 at Los Angeles, CA. Museum. 1334 at George Izay Park, Burbank. 57-1335/1417 Cancelled contract (believed for F-104D)