Explanation:

Her parents have arrived at the airport.
"On" is used to indicate position, usually indicating that something is on top of something else. We might say, "My journal is on the desk." In this function, "on" typically denotes proximity or position. Another example would be, "He sat on the stone wall."
The preposition 'at' is used when referring to buildings as locations in a city. This can be confused with the preposition 'in'. Generally, 'in' is used with buildings to mean that something occurs inside the building. 'At', on the other hand, is used to express that something happens at the location