I recently used my Garmin 60C on my flight from Singapore to Bangkok. The bag with the 60C went through the X-RAY machine without suffering damage (except for the weird look on the security officer's face). Reception was good on the plane but I lost reception when taking off and while I was eating (the GPSr has to be at the window at ALL times!). Moving it more than 4 inches away from the window will result in loss of reception.
For a list of airlines and other stuff about using your GPSr on airplanes, check out this great website:
GPS information