Remember, no one can give an assurance of prompt and on-time delivery. All shipping options come with a specific delivery timeframe, but these times are just placeholders. They give you a rough idea of when the parcel will reach. Of course, all shipping services try to stick to these timeframes. But any unforeseen event can force the delay. So, the first-class option can take more time. It might happen because of possibilities that cannot be changed, like bad weather.