From charlesreid1

Previously, with Kali 1.0, I could put my USB wireless chips into monitor mode and start a pcap dump by running the following sequence of commands:

$ airmon-ng
$ airmon-ng start wlan0
$ airodump-ng wlan0

However, after changing to Kali 2.0, I had to change the way I called the commands. I had to put the chip into monitor mode with the following commands (see https://taufanlubis.wordpress.com/2010/05/14/how-to-fix-ioctlsiocsiwmode-failed-device-or-resource-busy-problem/):

$ iwconfig
$ ifconfig wlan0 down
$ iwconfig wlan0 mode monitor
$ ifconfig wlan0 up
$ airodump-ng wlan0

In case of problems with rfkill: Rfkill