All - I'm a UK passport holder with GE - arrived at IAH from LHR a couple of days ago - used Global Entry and got my GE slip - Customs guy then took my slip off me. I queried it at the time and was told all GE slips are collected at port of arrival. Leaving the US now via EWR and I'm curious - how does the US Gvmnt know I'm leaving the US? Is it via ESTA linked to my flight details somehow ? Is ESTA linked to GE ? Do I even need an ESTA visa ? Just a bit confused as I thought I was supposed to retain the white slip and hand in in departing the US. Gate Agent has no idea.