airport utility does not show time capsule

We don't want to waste your time asking you do things that you have already done or tried to resolve the issue, so could you please list the troubleshooting steps that you have already performed?

It would help if we knew what operating system that you are running on your MacBook Air. If you are not sure, click on the Apple icon in the upper left corner of the screen and then click on About This Mac. Post back with the first few lines of information that you see there.