[xeromal]

Sometimes monopolies exist because it's extremely hard to succeed even if no one is stopping you

[Iulioh]

The concept is called "high barrier of entry"

[xeromal]

I'm sure airplane manufacturing falls under the highest barrier to entry besides maybe space exploration

[ben_w]

Boeing merged with one of their competitors, and now outsource to subcontractors; both of these suggest the barriers, high though they are, are not insurmountable.

Also, the FAA could ask people from Lockheed to mark Boeing's homework.

After a bit of Googling, looks like the FAA do also get Airbus to do this to Boeing, despite Airbus being famously not American: https://www.reuters.com/business/aerospace-defense/airbus-wi...