The cabin crew is distributing drinks to passengers.
Tips
usage
Short for 空中乘务员. 空乘 covers both the role and the major you study at airline academies. In casual speech, women may also be called 空姐 (air-sister) and men 空少 (air-young-man).
memory
空 (sky) + 乘 (ride / passenger) - literally sky-ride staff. The same 乘 reads chéng as in 乘客 (passenger), not shèng.