Based on my experience, it largely depends on time of day and where you're going.
For example, late evening domestic flights tend to have a lower "show" percentage since people misconnect, get stuck in after-work traffic, etc. Also, red-eyes to the east coast have a higher no-show since people list for multiple flights even though they're not supposed to, trying to cover their bases and get on whatever they can (LAX
You're right that it's much higher for int'l flights. In this case, it depends on frequency. You're going to have a higher percentage show for a once-a-day flight (ORD
, for example) than if people know they have a backup (3x IAD
, for example). I would speculate that the percentage is probably in the 75 % range, but again that's mere speculation based on my fair amount of experience.
If there are multiple flights, always show up for the first one since you have a better shot with misconnect revs and non-revs. Keep in mind that tonight is the start of a 3-day holiday weekend in the U.S.
What airline/route are you planning on, if you're comfortable sharing?
"We hope you've enjoyed flying with us as much as we've enjoyed taking you for a ride."