I have a Droid 3 on T-Mobile. Since the D3 only gets EDGE, I bought a myTouch 3G to use as a wifi hotspot. I turn the phone off and swap the SIM. If I turn on the D3 with no SIM card when it's not in airplane mode, it tries to switch the CDMA antenna on and causes an error in com.android.phone to pop up repeatedly. I had to restore a backup to get it working again.

I found if I power on in airplane mode it's not a problem. A couple of times I've powered the phone down and removed the SIM, only to realize I forgot to turn on airplane mode. I have to wait for the phone to boot back up to shut off the antenna. One of these days I know I'm going to forget and the problem will happen again. So I'd like to automate the process and have the phone go into airplane mode automatically when I power it off.

I know you can do it using the Tasker app, just trying to see if there's a free method out there.