Here are Delta's exact words on the subject:

"The recommended arrival time at the airport prior to departure of international flights is 3 hours. When traveling to/from a destination outside the United States, you must be checked in at least 60 minutes before your scheduled departure time and it is required that originating passengers be at the gate and ready to board at least 45 minutes before your scheduled departure time. This minimum requirement applies to all customers checking-in, with or without baggage. Customers who fail to complete the check-in procedures by these deadlines will not be able to travel on desired flights and change fees may apply."

Much of this to cover themselves for the constant changing security worries. Wednesday at STT in late spring is probably not an issue. The real time limit is your bag(s) must be fully checked in with the computer tag printed and bag on the belt at the 60 minute cut off. Many arrive on the airports grounds well ahead of the 60 minute mark only to find themselves still standing in line at the cut off time. Standing in line to check in is the same as not being there. On STT some days (mostly Saturdays) the lines to check in and the lines to get through all the security can be daunting.

Consider did something happened on a plane this week. We have no idea what security will be next week. That is true every week so the airlines suggest planning to be at the airport 3 hours ahead of your plane.