Pasażerowie o ograniczonej mobilności = Passengers with reduced mobility. The construction 'pomagać w' is quite natural, i.e. Pomogę ci W ODRABIANIU pracy domowej - I will help you to DO your homework. You stress the fact of EXECUTING an action. Pomogę ci Z pracą domową - 'I will help you WITH the homework' is also correct. 'Pomagać o' - I haven't heard about such a phrase, it sounds unnatural.

I think the "o" here can be best translated as "of". Ie. Ludzie o wspólnych zainteresowaniach. People of common/mutual interests. Pasażerowie o ograniczonej mobilności. Passengers of limited mobility. So: Pomagać ludziom o ograniczonej mobilności = to help people of limited mobility. I find this translation suggestion superior, since it can be used in broader context ie: Myślę o Tobie I think of (=about) you Książka o owocach Book of (=about) fruit Ludzie o polskich korzeniach People of (=with) Polish roots Etc.

The question here is quite old, but I think the answer marked as the best isn't complete. ... pomagać pasażerom o ograniczonej mobilności .. - the construction here is a verb (bezokolicznik / infinitive) + compound noun: infinitive/predicate - pomagać compound noun/subject - pasażerowie -O- ograniczonej mobilności (passengers -WITH- limited mobility) I believe "o ograniczonej mobilności" is adnominal modifier here. The full translation would be something like this: During the flight staff isn't obligated to help passengers with limited mobility with eating or taking medicines. "O" has a lot of meanings in Polish. It isn't always equal to "About" (myślę o rodzynkach - I think about rasins). It is sometimes used to clarify or give more details about the subject. Llike here - passengers o/with xyz or osoby o polskich korzeniach - people with polish roots. You could say osoby z polskimi korzeniami, but that means changing grammatical case (z kim, z czym? - Narzędnik /instrumental case). You can use it to answer when you have to meet with someone - "o piątej" /at five o'clock). It is also an expression (o! widziałeś to?! - oh! Did you see that?!) and the question for the last grammatical case - Vocative (O! Książę / Prince!).