The 18-135 is my 'walk-around' lens. I find the FL range is ideal.
Here's a 100% crop shot, one of the US Navy's Blue Angels taken last week. The plane was approximately 1/2 mile away and going perhaps 300 mph. The image of the plane is 275 pixels in length out of 5184 pixels full frame. A 50 mm lens might give you 100 pixels to work with.