aeroplane blonde, n. — Green’s Dictionary of Slang

aeroplane blonde n.

also airplane blonde

[pun on SE black box/box n.¹ (1a), i.e. her pubic hair is still black]

a woman with dyed blonde hair.

1999		Roger’s Profanisaurus 3 in Viz 98 Oct. 3: aeroplane blonde n. A darkhaired female who dyes her hair blonde, i.e. is equipped with a black box.
2001		P. Meditzy ‘A Day In The Life Of...’ 29 Apr. 🌐 Then I caught the eye of this ‘airplane blond’ (one who had dyed her hair but probably still had a black box).
2002		Fantasy Girls UK 🌐 Joanne Guest is a British glamour model – [...] She’s got brown eyes, Hair – blonde (aeroplane blonde: blonde hair, black box!) weighs around 120 pounds (or thereabouts).