The video "How GPS Spoofing Could Bring Down an Airliner" from the YouTube channel "CyberGuard Essentials+" explains the real-world threat of GPS spoofing to airplanes. GPS spoofing involves sending false GPS signals to trick devices, including aircraft navigation systems, into believing they are in a different location. This dangerous practice can cause planes to deviate from their intended paths, potentially leading to dangerous situations and delays. While airlines and safety officials are actively developing technology to detect and prevent GPS spoofing, it remains a significant concern due to its potential for disruption and harm.