This is the 10069th most frequent Russian word.
аэроклубу
"Aэроклубу" is the dative form of "аэроклуб," meaning "to an aeroclub" or "for an aeroclub" in English.
The word 'аэроклубу' is in the dative case, indicating the recipient of the action.
Вчера мы отправили письмо аэроклубу.
Yesterday, we sent a letter to the aeroclub.
Here, 'аэроклубу' is also in the dative case, showing that something is being beneficial for the aeroclub.
Его знания о полетах пригодились аэроклубу.
His knowledge about flying was useful to the aeroclub.
In this sentence, 'аэроклубу' is used in the dative case to specify who is receiving the gratitude.