Deadheading
Solo
Yes, passengers is a plural common noun, a word for any passengers anywhere.
The plural possessive form is passengers'.
There were forty passengers waiting in line for the next boat.
Stewards, and some officers, were dispatched to alert the passengers.
The noun 'passengers' is a plural, common, concrete noun; a word for people.
Yes, the noun 'passengers' is a concrete noun, a word for a group of people.
many passengers were still inside. He shouted at me.
Archimedes Principle
board passengers are given a boarding pass
board passengers are given a boarding pass
The car owner's policy would cover the passengers' injuries. But if the car was used without permission -- that is, if the unlicensed driver just took the keys without asking - then the insurance company is unlikely to cover any claims.
The flight attendant helped the passengers to their seats.