乗客 is used for passengers on public transportation.
COMMON COLLOCATIONS:
- 乗客数 (number of passengers)
- 乗客を乗せる (to carry passengers)
- 乗客名簿 (passenger list)
COMPARISON:
- 乗客: passenger (general term for public transport)
- お客さん: customer/passenger (polite, service context)
- 搭乗者: passenger (aviation, formal)