One of my clients used to joke about their business delivering on the 37th of the month, meaning that they missed their end of month delivery dates by several days.
I still smile when I think of this phrase, especially when I am helping new clients overcome their scheduling issues.
A lumpy order book that isn't managed properly is one of the main causes I have found to affect on time delivery performance. The fix isn't too difficult either, spend some time to reschedule the order book so that you can give your customers a realistic delivery plan going forwards.
Slightly more tricky is ensuring your business doesn't get back into the same position by changing how you accept work into your order books in the first place.
This is something we discuss in 'Business Process Re-Engineering', available on Amazon, and a great place to start if your on time delivery performance isn't where it should be.
Author, Consultant and Chartered Engineer