Originally Posted by: zreynoldsp... Mr LordatheStrings - I've always slackened my guitar strings, previous wisdom having been that they'll break with the change in air-pressure. Is this a myth?

Myth. With the strings slack, the truss rod is unopposed in bending the neck back. For a day or so, with gentle handling,that is unlikely to cause prroblems. It can't be good for it to have that kind of tension on the neck while its getting bashed about during shipping.

Air pressure change? Regardless of what the absolute value of the ambient air pressure happens to be, that pressure will be equal on all parts of the guitar. Temperature is another matter, though. The baggage hold under the aircraft is unheated, and it can get damn cold in there. Even so, the neck is less likely to do something strange if it has its normal balanced tension on it from the strings and the truss rod.

I've bought several guitars on eBay, and I always insist that they be shipped with the strings tuned to pitch. All of them have arrived with the strings still in tune. I take that to be evidence that the guitars were undisturbed by whatever conditions they encountered during the trip.