If your ticket allows a stopover, an upgrade voucher will (in most/all?) cases not!

UA's stopover definition on an international ticket (starting or ending outside Mexico-Canada-USA):

whatever is longer than the following is considered to be a stopover:[*]the next flight to your next destination on the same ticket (even it is way more than 24 hours) [*]>23 hours 59 minutes, but there is one day/night per calendar year where this time is extended to 24 hours 49 minutes ... and another day/night where it is shortened to 22 hours 59 minutes.

And this rule was always applied by UA on all my multiple InnerNorthAmerican Segments on my StarAlliance rtw-trips: I often even included a short night in SFO or other places, but kept they stay just under 24 hours, and was succesfull so with only one upgrade voucher.

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[This message has been edited by Rudi (edited 11-21-2000).]