Board Thread:Questions and Answers/@comment-89.160.79.11-20130206124147/@comment-173.71.27.18-20130208101646

Weight is a huge factor in whether or not you can fly with the jetpack module. If you have diamond plating on all your armor pieces, there is no way you can get off the ground with the jetpack unless you only fly straight up.

By default, you fly by holding the spacebar.