Yaris AIR BAG Passenger light - explanation needed

[Abk911]

There is something that is confusing me in my wifes toyota yaris 2008 sedan. Usually only wife drives it.

the "passanger airbag" light section seems to have 4 lights: (not in the speedometer / fuel gauge panel) these lights are under the word "Passanger" written on the dashboard.

1) AIRBAG
2) OFF
3) ON
4) passanger seat belt (ignore this light as this is not an issue for my query)

When you start the car 'alone' the 3 lights come - airbag, on , off then the "ON" and "OFF" light dissapear, but the AIRBAG Light remains lit - always. Is it normal for the AIRBAG light to be always on. If its normal why is it usually lit, shldnt it go off?

Wife usually drives it and not sure if she noticed it before. I noticed it as i dont usually drive it and hence want to know if its normal.