Originally Posted by ptonwind

It depends which airports you fly through. I've found MAD, LIS, and RAK to be particularly bad for losing bags ("lost" as in "gone forever"). On two separate occasions, one of my traveling companions lost bags while connecting through MAD (one time the lost bag contained very important product prototypes). Though, both occasions in MAD were with Spanair, not United.

I've argued my way into the luggage storage area of LIS after a very important bag was delayed for five days with no explanation of its whereabouts. I found my bag hidden in the carnage of lost bags. If I hadn't gone back there, I suspect my bag would still be rotting with the others. But the amazing part of the story is not that I found my bag but that it still had its tags.

So, I feel checking bags should be a last resort. Bags can get lost even when properly tagged, making the probability of loss arbitrary.