Question

Passenger's concerns about cell phone use on planes are justified. I am trying to find the in the errors in possesive consruction of the above sentence. The ' either need to go all together or it needs to follow the s in Passenger's. Revised

Answer 1

If you remove the 's (the apostrophe and what follows), what are you left with? That is, how many passengers -- one or more than one?

That tells you whether the apostrophe is in the right place or not. The noun has to correctly reflect the number of people involved (only one, or two or more). If it doesn't, then the possessive construction is not correct.

one passenger ---> one passenger's concerns

two or more passengers ---> two or more passengers' concerns