The Global Entry application asks for your passport information in addition to your Green Card, even though technically speaking you only need a Green Card to enter the US. Does this mean one is required to carry a passport when flying into the US or can you fly with just your Green Card and your Global Entry card?
As for scenarios where this could matter: you can fly to Canada and back with just your Green Card. You can likewise fly to the US from the UK with just a Green Card, as the UK doesn’t have exit immigration. Finally, EU citizens can fly to the EU with just their national ID card and then return to the US with just their EU ID card and their Green Card.