"There are one hundred people on the airplane."
Translation:Υπάρχουν εκατό άνθρωποι στο αεροπλάνο.
I thought the "ν" was added before a verb starting with a vowel?
For masculine and feminine accusative, yes.
But αεροπλάνο is neuter -- and neuter words always look the same in the accusative as in the nominative. In all Indo-European languages that I know of. (Even in English -- we have he/him and she/her but it=it.)
Thus (σ)το αεροπλάνο.