The rear aircraft is 51-1828, the YRF-84F Thunderflash prototype, first flown in February 1952. As you can see, the second YF-84F Thunderstreak, 51-1345, also had side intakes. These gave some loss of thrust and were not adopted on the basic F-84F. Seen flying near Edwards AFB, both aircraft still have the old canopy of the Thunderjet. Photo from: US Air Force

Originally designated YF-96A, it featured the fuselage of the last production F-84E fitted with sweptback wing and horizontal tail. Note the round intake of the f-84E as opposed to the ovular intake of production F-84Fs. The change was required to accommodate the increased airflow needs of the more powerful J65 engine which replaced the J35 of the F-84E and YF-96A.Iit's last use was in the development of the FICON parasite fighter for the B-36 with the addition of a nose hook and negative dihedral on the horizontal tail surfaces.