Good excuse for missing class

Raytheon does after hours classes if you have a particular subject you'd like to learn more about. I'm currently in a class about Kalman filtering. The instructor is a man who has worked here for many years and had a lot of hands on experience with Kalman filters. He's also taught the class many times previously. Anyway, the first day of class he was explaining what is required to "pass" the class, attend a certain percentage of classes and turn in a certain percentage of the homework. He then proceeds to say that we shouldn't stress about missing a week of class for a vacation. He said "I consider vacation a perfectly good reason for missing class". Now only if my professors at college had felt the same way!