An occupied bedroom with poor ventilation can get that high. Being on an airplane at that level for a few hours once in a while isn’t going to cause any problems.

That said, people should probably be more concerned about co2 levels in their homes. At night, I crack our sliding glass door open and put a fan next to it, and run the central air fan. It keeps co2 levels at like 600-800 depending on the room. Super easy fix.