Proper planning is the key to a successful project, but of course, there are a few problems beyond the realm of planning as it is not always possible to predict what would happen after a project starts.
One of the major problems is the cost overrun. Besides the underlying nature of massive and complex projects, poor execution of project management leads to increased costs. A good project management team must be capable of identifying the possible sources of cost overruns early and mitigate their effect.