Unless the vehicle has a little "airbag" trouble light on the dash that remains on.
Some vehicles may even have a "service" light that will stay on if there is a fault present in the airbag circuit, which there would be if the bags were completely missing.
I don't if all newer vehicles equipped with air bags have the system integrated in the computer controls or not, although I would imagine most do.
I had a friend who's Saturn was missing the air bag and it caused a trouble light to remain on in his vehicle. But at about $1,500.00 per air bag, he didn't let the light bother him at all, he would just say that he had complete faith in the seat belts,,,,,