At the front of the cowl, the cover of the air intake is recessed, and has a rounded shape. You don’t need to make the model as detailed as an actual airplane would be, but these steps give the general look of the front of the plane.
This makes it easier to see the polygons with which you’re working.
You can also see this change in the Left viewport.
Release the mouse, then drag it downward again a little bit, to taper the inside of the recess. This change is easier to see in the Left viewport.
As for most of the P-47 model, exact distances don’t matter here: The important thing is the overall look.
Even with X-Ray display, it is a little hard to see details of the blueprint image.
Here is the image without the geometry in front of it:
(If you like, you can also choose Rendering View Image File, and then open \sceneassets\images\p47_front.jpg to see the full-size version of this image.)
As the blueprint image shows, there is a circular area within the recess: This is the intake for air to help cool the engine. The air intake for the engine’s combustion is a pipe located below the circular area.
If you activate the Perspective viewport and press Alt+X to turn off X-Ray display, you can get a better view of the work you’ve just done.
The front of the airplane is nearly done, for the time being. But because of the way 3ds Max constructed the cylinder that was the origin of this model, the intake face is a 10-sided polygon. As we mentioned earlier, it is best if the mesh consists of consistently quadrangular polygons: These work much better with smoothing and (if you are creating a character) with skin deformation. So to complete the air intake, you divide the large 10-sided polygon into smaller quadrangular polygons.
It is hard to see the connecting edge until you click elsewhere in the viewport to deselect the initial vertices.
Now the original 10-sided polygon is divided into four polygons, and each of the new polygons has only four sides.