If you see a blue GPS icon in the upper right of your iPad or iPhone screen, that icon is letting you know that GPS location services are being used while the app is in the background. If you tap on the icon, it will open ForeFlight.
Blue location services icon
This icon will only show if you have the Location Services setting for ForeFlight set to WHILE USING THE APP and a Track Log is being recorded in ForeFlight. The Location Services setting is found in the iPad or iPhone Settings App under FOREFLIGHT > LOCATION. If this setting is set to ALWAYS or NEVER, this icon will not be seen.