[sddfd]

No, they don't. New variants enter the market, such as the 737 MAX, which are easier to certify.

Boeing introduced the last new airframe for commercial passenger transport on 2009 (the 787). Before that, it introduced the 747 in 1994.

Which new airframes that enter the market all the time are you talking about?

[jacquesm]

The 737 MAX is a new plane, they hacked the type certification process to get around that.