I never noticed the extra door behind the wing on the B739ER, the only 900s I see are United and the door has the large window and doesn’t have the grey stripe to identify it like a regular door or emergency exit…
flightaware.com/photos/view/8923 … tes/page/1
Then there is this version, the door has a small circular window and the grey stripe around the door…
flightaware.com/photos/view/1147 … tes/page/1
I thought all exits had to be marked with the grey stripe, or does United not consider that an exit?
Depends on the seating configuration. According to seatguru UA’s 739s are 167 in 2-class + plus 
whereas Lion’s are 200+ single class.
Lion needs the extra exits, UA doesn’t but I suspect they are installed anyway for future flexibility.
That makes sense, thanks!
I wonder what they (UA) look like from the inside?
Two missing windows.
The “extra” door is only for emergency use. Some airlines will disable them as long as all 4 overwing hatches function.
From what I read online the 900ER was built to compete with the A321, the A321 has 8 large doors and no over wing exits.
Why wouldn’t 4 large doors and 4 smaller over wing exits work for the 900ER with the 200+ pass. load? FAA regs.?
The evac rate of an overwing exit isn’t the same as a door. See 14 CFR 25.807.
If Boeing would just install roll down windows you could get everybody out in 8 seconds…
That would be a terrible idea lol