Is mileage a variable cost?

• hard drive recovery cost
• hard drive data recovery cost
• visa air miles

I am doing a project for college, I work for a coach hire company and they wish to expand their business and start offering coach holidays and I have to create a set of budgets etc to see if this will work or not and one of the things I have to do is list all variable and fixed costs and was wondering if mileage is considered a variable cost?

Additional Details

Mileage is charged at £0.50 per mile, does this make it fixed? Or is it variable because the number of holidays per month varies?

Is mileage a variable cost?