Originally Posted by iahphx

With a 3-4-3 configuration (or something similar), your best shot at having an extra seat free is to book a window and aisle, and hope the middle stays free. The odds are somewhat higher if you're an elite member and can do this in "elite seating," as those will typically be the last seats filled on an aircraft. You further increase your odds by flying at off-peak times -- and mid week -- when load factors are lower.

All that said, your odds on most int'l flights aren't great, except for those off-peak flights. Load factors in the industry are particularly high now, and int'l flights tend to have even higher load factors than domestic flights. That said, this strategy does sometimes work, and there's very little downside risk (the person in the middle seat will happily switch).