The abyssal version of Aircraft in Kantai Collection. Unlike the shipgirl aircraft, which tend to be miniature replicas of real World War II-era Imperial Japanese Navy aircraft, abyssal aircraft have the alien appearance of Abyssal Ships.
They usually look triangular from the top, with a black metal skull-like appearance. Underneath, they have cannons sticking out of their "mouths" or have bombs or Torpedoes strapped underneath. Some, notably those launched by Northern Ocean Princess, have a more Takoyaki-like spherical look, and are white with red highlights.
Not to be confused with the spherical and eyeless Floating Fortress (Kancolle) or Escort Fortress (Kancolle).