I don't know how hardened aviation GPS is, but the OfCom website has an interesting piece on loss of service, presumably only in the UK.
From
http://www.ofcom.org.uk/static/subsc...elect_list.htm
GPS Jamming
The Ministry of Defence conduct occasional tests on military systems which may result in some loss of service to civilian users of the Global Positioning System (GPS) including in-car navigation devices and networks which rely on GPS signals. Ofcom seeks to provide citizens and consumers with information about possible interruptions to these services via these email updates giving advanced notification of these tests. It must be emphasised that this notification process only warns of future jamming excercises that are brought to the notice of Ofcom and may not cover all jamming exercises. It cannot be assumed that any loss of service is due to jamming exercises.