Keep in mind that not all of the following measures are applicable in all instances, thus, emphasising the importance of identifying the causes for the schedule slippage.
You can then take the appropriate action or series of actions.
For example, in case of specific tasks causing the delays, the better action is to add expert resources but when artificial task dependency is the one causing the delay, then eliminating it is the better option.
In this way, the project’s tasks can be done simultaneously instead of a sequence, thus, fast tracking the achievement of the desired results.
Perhaps the project is off schedule because of ineffective and inefficient allocation of resources, such as when the wrong people were assigned to the tasks or when the budget was insufficient for the jobs.
While you may have carefully studied the personal traits and professional qualifications of your team members before task delegation, you may have committed a few mistakes along the way.