When flying any of the training missions, you need to be very close to the gates before they become visible. This leads to them suddenly popping-up out of nowhere.
As an aside, if somebody is going to be looking at this, it would be extremely useful to have a trigger to turn the gates off, rather than only having one to turn them on.
For example, if I want to practice circuits, I want to fly the circuit without the gates on, but it would be really helpful to switch them on for a short period to check where I am in relation to where I should be.