Okay so let's calculate this. The function for flying is $ = (number of people) (flight price) + (rental car price) (number of days spent) + (gas) + (cost of airport parking) The function for driving is $ = (number of people)/2 [rounded up to nearest even] (2) (hotel price) + (gas) So consider a ski trip to Aspen from March 17 to March 24. American Airlines charges $362 to fly to Vail (flying to Aspen is more expensive and a lot of people don't do it). I'm going to add on say $100 worth of gas for the drive to and from Vail along with driving in Aspen for the week. The average rental car is about $500 from Hertz for the week from their Vail-Eagle lot. A week of remote parking at DFW is $56. So we have the variable x representing the number of people $ = 362x + 500 + 100 + 56 $ = 362x + 656 For driving will assume that you get 20mpg with gas prices at $3.65. It is a 869 mile drive to Vail. x represents two people because that's how many usually stay in one hotel room So 1 to 2 people would be x = 1, 3 to 4 people would be x = 2. A budget hotel room in Amarillo is $50, I’m assuming you sleep there both ways. I’m also adding on the $100 for Vail to Aspen and back. $ = x (2) (50) + (869/20)(3.65) + 100 $ = 100x + 158.5925 + 100 [I’m going to round up the penny] $ = 100x + 168.60 So to summarize, it costs a lot more to fly to Aspen (well Vail) than it does to drive to Aspen. I really thought that gas would cost more. I wish that flight cost was determined only by miles flown. Then I could find the interception point between flying and driving. I could then color a map to show where it is cheaper to fly and where it is cheaper to drive. That would be neat.