The ungainly Northrop P-61 Black Widow has the important distinction of being the only purpose-built Allied night fighter of the war, ironic considering than the lesser need for such aircraft by the USAAF. Large and sinister-looking, it was very effective in that role especially considering how slow the US had been to adopt night fighter technology compared to the British and the Germans. This new twin-boom and twin-engined aircraft was equipped with airborne-radar developed locally from British designs though problems with the radar unit delayed service until 1944. Despite this, P-61s were very effective especially in the Pacific where they were deployed to protect B-29 bases in China and India (P-61s also served in Europe although in lesser numbers). Its menacing name was born out of the prominent all-black finish which characterized many units.

The prototype XP-61 first flew on 21 May 1942 and entered service as the P-61A. Additional refinements led to the P-61B night intruder which was deployed beginning in mid-1944 and was characterized by a lengthened nose and provisions for a considerable bomb load. The final variant was the P-61C with powerful 2,800-hp R-2800-73 engines though other late-war adapations were produced, these included the P-61G unarmed weather reconnaissance aircraft and the F-15A photo-recon platform.