Not knowing the specific routing or details of each flight, however it may have something to do with the arrangements between Ireland and the US for over flights of military aircraft.
No US military aircraft can enter Irish airspace without a prior request and approval (Ireland being a netural/non-aligned country) and the aircraft must meet certain stated conditions (e.g. not armed or carrying arms).
Perhaps given the current situation on the Gulf, the US has decided to not make declarations regarding any military aircraft on T/A tracks so they are all being pushed north to avoid Irish airspace and the UK is keeping then from poulation centres.
JAS
Last edited by Just a spotter; 6th Jan 2020 at 08:53.
Reason: typo