Cracked screen covered under warranty?

If you have AppleCare+ (the extended warranty) you have two accidental damage claims you can use to reduce the out of warranty fee for accidental damage. Otherwise, the full out of warranty fee applies.

Warranties cover defects in parts and manufacturing. Insurance covers things like loss, theft, accidental damage, etc.

Here is screen repair information (including pricing information).

iPhone Screen Repair & Replacement - Official Apple Support

Here is Apple's iPhone warranty (in the U.S.).

Apple One (1) Year Limited Warranty

It warranties against manufacturing defects. These typically do not include a cracked screen.