Multiple answers are allowed. If it's an industry, put 'Industry:', and then your idea. Example: 'Industry: [Your Idea]'
If I had to choose, I would say 'Industry: Airlines'. My reason is because there's 'Industry: Public Transport', which refers to transportation owned and operated by government/state operated services, it would be cool for there to be something for privately-owned and run transportation industries, and airline companies fall into this category.
What would you guys choose?