Does airplane-mode disable GPS? According to

http://support.apple.com/kb/ht1355


airplane-mode on the iPhone shuts off Wi-Fi, Bluetooth, ...GPS.  

My understanding is that GPS-devices only /receive/ GPS
signals, they don't transmit anything, so I don't
understand why this needs to be shut down.  [Of course, if
the iPhone is running at all, then /it/ is emitting some
RF, but I don't see why receiving GPS signals should cause
an additional problem for the airplane.]

I tested on an iPhone 3GS (IOS 6.1.3):  Enabled
airplane-mode, then turned-off the phone.  Rotated the
phone 180-degrees.  Turned it back on (with airplane-mode
still enabled).  The compass-app still seemed to find North.

Would someone be willing to do an independent test of this?
Yes, airplane mode shuts down the radios that amplify all antenna circuitry. Compass isn't affected by airplane mode other than not being tuned by GPS location. Your observed relative changes will be mostly unaffected but absolute accuracy could suffer between one and ten degrees on much of the globe. 

Of course the GPS signals still hit the iPhone case and antennas, just the hardware doesn't do the work to fix a location from those signals while in airplane mode. (Nor does e software do any processing of the location updates which is a big part of the functionality for many people as opposed to the hardware side of the radios being idle / off / silent)