The article ends with: > Are there any easily deployable defences? > No. > All of the backup systems, including GPS, fail to provide sufficient security guar

The article ends with: > Are there any easily deployable defences? > No. > All of the backup systems, including GPS, fail to provide sufficient security guarantees, and even supporting cryptographic authentication on ILS signals would still leave systems vulnerable to record and replay attacks. So seems solving with GPS is not enough.