Are planes considered boys or girls?

Planes are considered girls.

Indeed, many pilots (especially military ones) call their planes "she", they grow attached to them, they love them, they take care of them, they dance together in the sky, they also like to show them off (e.g. Vichy French pilots showing off their planes to ladies in 1940 North Africa)

An old veteran pilot always loves to see the old girl he flew with, this is because many pilots (especially of famous planes like the Spitfire) form such a strong bond with their planes they never forget the bond they share, it's a life-long love.