From: Rabbi Moshe Sofer
To: Rabbi Ber
A yevamah bound to brothers-in-law sought chalitzah, but the eldest yavam was some forty parsaos away in Hungary with no certainty of appearing. The Chasam Sofer ruled that the eldest of the younger brothers present should perform chalitzah immediately, on multiple grounds: the Mishnah in Yevamos explicitly prohibits delaying chalitzah for an absent elder brother, both the Bach's criterion of a different country and the distance criterion apply here, and the principle of zerizin makdimin demands seizing the certain present opportunity over an uncertain future one.
Source: Shu"t Chasam Sofer EH II §81