How can you rescue a slipping project and bring it back on track?
One technique to protect yourself from a failing project is to run, fast, like a rat from a sinking ship. It's not very professional, though!
Once a project is behind schedule, there's rarely anything you can do to bring it back on track—that is, unless there was a monster amount of contingency allocated. You might instead consider these strategies:
Reschedule the project; see if you can agree a later delivery date with the customer.
De-scope the first release, possibly agreeing to a later release with the missing functionality. It's better to commit to doing less stuff, but doing it better and within the allotted time, than to ...