JB standby?
 

I have a flight coming up and will call 24 hours before to see if I can do the standby for the prior flight.
My question is, if I get a go ahead when I call, what are the chances of not getting on the earlier flight? Does this happen often?
Thank you.

You are permitted to fly standby for free on the immediate prior departure (even if it is a connecting routing that arrives after your originally scheduled flight). For any other flight option the same calendar day it is a $40 fee and subject to space being available.

More information can be found in these two recent threads, among others:
http://www.flyertalk.com/forum/jetbl...er-flight.html
http://www.flyertalk.com/forum/jetbl...y-standby.html

I'm sorry I was not clear in my first post, I appreciate your time.
What I am wondering is, when I call for the free standby and they give me the OK to go to the airport (earlier) what are the chances of not actually being able to get on the prior flight?
Thanks again.

Flight loads vary from flight to flight, day to day, so it's difficult to know your chances of making it on standby. It's pure luck from the customer's standpoint since we do not disclose loads to the public. The good thing is that our airline does not oversell flights.

Thank you Jax.