I am making a few trips from the US to Europe in the next six months and want to take a bass guitar with me. I know that some people attempt to carry-on, with the backup of a gate-check. However, the instrument exceeds the 45 linear inch maximum before putting it in a case, and I don't want to rely on a rule being bent.

So I'd rather check it, using an ATA-spec case. This is definitely going to exceed 62 linear inches.

The UA.com 'Checked Baggage' and 'Excess Baggage' pages...
https://www.united.com/CMS/en-US/tra...geChecked.aspx
https://www.united.com/CMS/en-US/tra...ageExcess.aspx
...seem clear that above 62 linear inches a $200 each-way 'oversize' fee is going to apply.

However, the UA.com 'Fragile Articles' page...
https://www.united.com/web/en-US/con...e/fragile.aspx
...implies that 'oversize' fees apply to musical instruments only when they exceed 90 linear inches. Specifically: "Oversize charges apply to musical instruments that measure 90 - 115 linear inches".

So my question: Do musical instruments get a special exception to the 62 linear inch maximum?

Incidentally, I know that this is basically 'at my own risk' activity. The instrument has no sentimental value, and if I really have to pay $400 per round-trip I'll likely buy one at my destination.