Originally Posted by
dxt55
I should have done the same as you! The Global Entry app said to enter it exactly as on my passport, and the Global Entry fields were for "Surname" and "Given Name" so I copied the "Given Names" on my passport that had both my first and middle names.
Now I'm probably going to have to update all my FF and ticket purchases to include my middle name with my first name, and hope that whether there's a space or not between them doesn't cause an issue.
If you're willing to risk not getting PreCheck one time, you could try leaving out your middle name on one ticket and see what happens. We don't know how their backend actually works (at least I don't); it's possible it ignores the second given name regardless of which field it came from.