A pilot's report of ADS-B traffic disappearing above roughly 1,000 feet AGL while flying with an iPhone 17 Pro Max paired to a Sentry receiver touches on a persistent point of confusion in the GA community: ForeFlight's handling of traffic data when a device has both a cellular data connection and an external ADS-B receiver connected simultaneously. The behavior described—traffic showing normally on the ground, then vanishing shortly after takeoff—is consistent with a known ForeFlight design decision rather than a hardware fault. ForeFlight has historically suppressed ADS-B traffic display when it detects an active cellular data connection on the host device, specifically to avoid the liability risk of pilots mistaking cellular-derived or blended traffic data (which can be delayed, incomplete, or inaccurate) for the low-latency, FAA-sourced ADS-B traffic feed. The concern is that a pilot could make a see-and-avoid or separation decision based on stale cellular data believing it to be real-time ADS-B, so the app defaults to hiding traffic when it can't guarantee the data source integrity.
This matters considerably to working pilots because traffic display is a safety-critical function, not a convenience feature, and any silent degradation of that display in flight is dangerous if the pilot isn't aware it's happening. A VFR pilot relying on ForeFlight traffic depiction for situational awareness in a busy Class D or Class E environment, or a Part 91 pilot self-vectoring around traffic in non-towered airport patterns, needs to know definitively whether the app is showing live ADS-B-In data from the Sentry or nothing at all. The ambiguity here—not being sure if it's a Sentry pairing issue, a Bluetooth dropout, an iOS 17-era connectivity quirk, or ForeFlight's cellular-suppression logic—is itself the problem. Pilots who assume traffic is being displayed when it isn't are arguably worse off than those who know they have no traffic display, because the former may reduce their visual scan believing the app has their back.
The practical fix pilots have converged on in the field, and what ForeFlight support has advised in similar cases, is to put the iPhone in Airplane Mode and rely solely on the Sentry's WiFi connection for both ADS-B position and traffic data, or explicitly disable cellular data for ForeFlight in iOS settings. This ensures the app treats the Sentry-sourced ADS-B traffic as authoritative rather than second-guessing itself against a simultaneous cellular link. Owners of newer iPhones with dual-SIM/eSIM configurations and always-on cellular backgrounding (a growing issue as iOS aggressively maintains connections for services like SOS satellite messaging and Find My) may find this cellular-suppression behavior triggers more readily than it did on older hardware, which is a wrinkle worth flagging for anyone upgrading devices mid-subscription without revisiting their EFB configuration.
More broadly, this incident is a reminder that portable ADS-B receivers and EFB software are not "install and forget" systems—firmware updates, iOS updates, and app updates can all subtly change how traffic is prioritized, filtered, or suppressed, and pilots who don't periodically verify their setup on the ground before a flight (or cross-check traffic display behavior against a known scenario) risk carrying an undetected gap in their safety net. As ADS-B, cellular, and satellite connectivity increasingly converge on a single handheld device, the industry will likely see more edge cases like this one, reinforcing the importance of understanding exactly which data source is driving cockpit displays at any given moment, especially as portable EFB solutions proliferate across Part 91, flight training, and even some Part 135 operations as a backup or primary situational awareness tool.