What writer is the common denominator for both Disney films, cars and planes?
Cars (franchise): Cars is a CGI-animated film series and Disney media franchise set in a world populated by anthropomorphic vehicles created by John Lasseter. Planes (film):  Despite not being produced by Pixar, the film was co-written and executive produced by Pixar and Walt Disney Animation Studios' chief creative officer John Lasseter, who directed the first two "Cars" films.
John Lasseter