The amount of air fares or air flight

My cousin asked me. What is correct? The amount of air flight is … or the amount of air fares is … Is it wrong to say the amount of air flight?

Are you talking about the number of flights, or the cost of the flight?

The cost of the flight

The cost of the airfare, the cost of the flight, or the cost of the air ticket.

None of your suggestions are right.