The proposal's reception in the federal transport portfolio was in marked contrast. A meeting with the department secretary and senior officers of his department and the Bureau of Transport Economics was to foreshadow an uneasy relationship that was to continue despite the ostensibly cooperative attitude of federal and state governments. The proposal had been sent to the federal Minister for Transport, Peter Morris, with comments reflecting his officials' opinion: it was not worth considering. Although Sydney–Melbourne was later identified as the fourth-busiest air route in the world (busier than any in North America, or any in Europe apart from Madrid to Barcelona) and the bureau had no firm data on transport markets in south-eastern Australia, its officials judged passenger fares would need to be set at a rate that would not be commercially viable. The bureau would not accept the French experience that the laws of physics (in which momentum is proportional to the square of the velocity) allowed much steeper gradients (hence much fewer cut-and-fill earthworks) than on low-speed railways. The difference in the estimation of earthworks was $2 billion – a significant proportion of the total cost of the project.