According to Smarter Travel, by not turning your phone onto airplane mode, your phone will attempt to make connections with the cell towers around it. Forbes reported, “If you don't put your phone on airplane mode during a flight, your phone will probably annoy a few pilots and air traffic controllers.”

If you don't put your phone on airplane mode, it continues to search for a signal by sending out increasingly powerful radio "bursts" to try and reach a cell tower on the ground. At 35,000 feet, your phone may see signals from dozens of towers simultaneously, leading to "network congestion" on the ground as the system struggles to hand off your high-speed device between towers. For the aircraft, the primary concern is electromagnetic interference. While modern avionics are heavily shielded, an active 5G or 4G signal can occasionally cause audible "clicks" or "buzzing" in the pilots' headsets, similar to the sound a speaker makes when a phone is about to ring nearby. This can be a dangerous distraction during "critical phases" of flight like landing when clear communication with air traffic control is vital. While a single phone is unlikely to cause a crash, 200 active phones could theoretically interfere with the plane's sensitive landing altimeters. In 2026, many airlines offer "In-Flight Cell Service" via an onboard pico-cell, but this still requires you to follow the crew's specific instructions to ensure no interference with the cockpit.