Looks like 14 is as old as you can go for that.Including the theoretical iridium satélite emergency communications?
Connect to a satellite with your iPhone - Apple Support
With iPhone 14 or later (all models), you can connect your iPhone to a satellite to text emergency services, request roadside assistance, message friends and family, and share your location — all while you're off the grid with no cellular and Wi-Fi coverage.
support.apple.com