Macbook Air mid 2013 with Mavericks stopped connecting to familiar wifi after 10.9.4 update
I would try to manually connect to network to see if that works.

Here are the steps how to do that using Terminal by copy/paste following:

Turn On

networksetup -setairportpower en0 on


Find

/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport scan


Connect

networksetup -setairportnetwork en0 WIFI_SSID_I_WANT_TO_JOIN WIFI_PASSWORD