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, iPhone 14 Pro, iPhone 15, or iPhone 15 Pro, you can connect your iPhone to a satellite to text emergency services, request roadside assistance, and share your location with friends and family — all while you're off the grid with no cellular and Wi-Fi coverage.
support.apple.com