Countries charge for planes to fly through their airspace even if the plane does not land. Different countries levy different charges, therefore plane companies consider a number of different routes and calculate the associated charges with each route. The formula used to fly over Europe is considered and an example calculation provided. The first problem requires students to substitute the correct values into the formula in order to calculate the flying charges for two different flights. The second problem gives the charge and the distance flown requiring the students to use the formula to calculate the weight of the plane. In problem three a second formula is then considered which requires students to look up relevant information from a table of data followed by three problems for students to complete. Problem four asks students to illustrate the charges using a series of graphs.