To be honest calling the police and saying you have a bomb planted on flight XYZ and want 100000$ or you'll detonate it, is probably also enough.
A completely-innocent Airtag speaks only bluetooth, and it can be activated from continents away -- as long as any Apple phone is nearby with a shred of Internet access.
My similarly-innocent Samsung phone is programmable (using its built-in Routines function) to perform actions in response to becoming disconnected from any given Bluetooth device.
Reliably bomb detonation is on the roadmap for Bluetooth 8.