HOW OLD ARE THEY?.........
2007 to 2019 worldwide. It’s mostly premium carriers that have the plugs installed. It allows the plane to carry 189 passengers which is the maximum certified for the 737-800, 737-900, and Max 8. To have more than 189 passengers, it is required to have another emergency door installed. The 900 and 900ER with plugs carry up to 189 passengers with more pitch between seat rows than the 737-800 or Max 8. This allows more premium seating to be installed.