Shaun Bosley, from Brighton, dropped a work colleague at the airport in November and received a £100 "final notice" from NCP several months later.
He turned to AI, using ChatGPT to generate a human-like appeal, saying he had had no previous notice of the fine.
Mr Bosley said NCP reduced the fine to £15, which was the original amount.
ChatGPT users simply type a request into a chat box and the system can generate a response almost instantly.
"In the end, I just typed, 'write an appeal to a penalty charge notice for driving through Gatwick Airport. I have received final notice, but never received first notice of the penalty', and straight away it came back with a great response," Mr Bosley said.
Motorists dropping passengers at Gatwick must pay £5 for a maximum of 10 minutes. They are charged an additional £1 for every minute they stay after that up to a maximum of 20 minutes.
ChatGPT helped him create the appeal which referred to the "undue stress and hardship" the final notice had caused.
It also asked NCP to provide "information regarding the circumstances" as to why Mr Bosley had failed to receive a first notice of the fine.