Originally Posted by
JimInOhio
Do you have a link to that 40 min. MCT? That seems way too short and from what I see on ExpertFlyer, the MCT (I to D) is 1:30. Regardless, the 2:20 your wife has is sufficient, especially since the inbound rush from most other Europe flights is much earlier than that later BA flight.
The 0:40 DD connection is only for some specific UA-UA connections. EF has the correct default ID MCT (90 minutes). As long as the BA flight is more or less on time, there should be no issue.
When the OP's wife clears immigration and customs, she will need to use the UA check in desks before she clears the sterile area. She can check her bags and get her onward boarding pass. It will make the transit a lot easier. She will be able to go directly to TSA security when she arrives at T3.
Since the arriving flight is on BA, I suspect she will be on separate tickets for her international flight as opposed to her domestic connection.