Possibly related: every 737 variant ever made is certified under the same FAA type certification. It's on at least revision 58: http://www.b737.org.uk/a16we.pdf

Possibly related: every 737 variant ever made is certified under the same FAA type certification. It's on at least revision 58: http://www.b737.org.uk/a16we.pdf http://www.b737.org.uk/a16we.pdf I have read on forums (but don't know enough to confidently claim personally) that Boeing changes as little as possible between 737 generations to keep everything under that same certificate. And that the 737 MAX would never pass certification as a brand new airplane; instead it's just considered a new variant of a 49 year old plane (and largely grandfathered into those regulations)