Originally Posted by
EWR764
Yes, not only is a STC required but the LOPA (Layout of Passenger Accommodations) must also be submitted and certified before installing the interior.
Here is UA (CO's) STC for the 737-900/900ER E+ reconfiguration:
STC
Cool, thanks! Just hadn't seen any prior mention of it and didn't know if it was a requirement or not when they pull out the row of seats and shift things around.