Originally Posted by
gizmo78
Whoops...I didn't realize you could mess with peoples reservations with just the PNR and the date. Thanks for all who pointed it out.
One can mess with a reservation if only the passenger's name, flight number and date of travel are know.
(The flight number is easy to figure out if you know the passenger's origin and destination. I still don't know why US hasn't closed this hole. I guess people don't mess around with others' reservations too often.)