A common challenge many clients face in project management is simply being able to get enough people onto the project team. To build crucial momentum, a successful project requires sufficient team members to take care of all aspects of the planning and execution.
What makes this problem especially insidious is that in some cases, it may initially appear that you have enough willing team members for your project. What becomes apparent as the project gets underway however is that a significant number of these members are already overcommitted on other projects and therefore unable to contribute fully in their role as intended.
This can also be a timing problem, where people assigned earlier to your project are unavailable at its commencement due to other projects they are involved in running late. Then there are the situations where recently completed projects fail, leading to emergency situations that occupy human resource, leaving your project stuck on the runway.