The flight attendant should never hand a _______ customer the beer can unless requested.

The correct choice highlights the principle of service etiquette and the distinction between different cabin classes. In the context of onboard service, First Class customers typically receive a higher level of personalized service. This can include more attentive interactions, where flight attendants gauge requests before serving drinks, rather than presenting items without prompt.

By specifically not handing a beer can to a First Class customer unless requested, the flight attendant respects their experience and maintains the elegant atmosphere usually associated with First Class service. This approach allows for a more tailored interaction, where customers feel their preferences and choices are valued, enhancing their overall flying experience.

On the other hand, in different service classes, such as Economy or Business, the expectations for service might be less formal, making it more acceptable to offer drinks proactively. Frequent flyer customers may receive special recognition and some benefits based on loyalty but do not necessarily align with the service standards applied to First Class.