This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. The しゅつ gets shortened and はつ changes to ぱつ. No wonder you want to make a departure, you want to get away from crazy readings like this.
There are five minutes until departure.
I'm going to leave for Tokyo in two weeks.
Thank you so much for inviting me to a drinking party to celebrate the departure of a co-worker that I rarely spoke to.