Via Consumerist:

According to the Bureau of Transportation Statistics, the worst flight in existence for delays, is US Air Flight 1543 (Boston to Charlotte) which is late 100% of the time, with the average delay being 53 minutes.

I for one have had delays 100% of the time on EVERY flight I have EVER taken with US Air, some nearly missing me crucial connections, so this is not surprising. However, since Charlotte is their hub, through which most US Air connections are made, it may be wise when flying US Air out of Boston, to build in some extra time to catch that connector.