an option on the airline's part. that is why to anybody watching a SW
737 landing, the only planes that were ordered with the logo lights were the new -700's. reason behind this, when southwest ordered the -700, they originally did not realize with the much larger wing, that at many of their airports, their gates were so tight, that the SW
gates could not handle the -700. when a -700 would arrive, it would help ground crew earlier on to see that maybe there was an equipment change and the now-700 instead of maybe the scheduled-300 would require a different gate, thus not allowing them to park where originally planned. first time this happened was when a new -700 arrived into PHX
on an aircraft swap, was pulling in, and took out two baggage carts. the carts were parked outside of the painted linesa and legal, but the much larger -700's wing compared to the schedule -300's wing hit the cart. many of the gates in PHX
now have red/white signs that say "NO 700" for that reason.