Casement Aerodrome in Baldonnel is primarily used by military aircraft, but occasionally civil aircraft are permitted to use the Aerodrome for, inter alia, the purpose of pilot training, familiarisation visits and landings of charter aircraft for Irish troop rotations.
I am advised by military authorities that KC-135 aircraft have never used Casement Aerodrome. However, I understand that KC-135 aircraft are similar in appearance to other aircraft such as the DC-8 cargo aircraft, which has recently landed at Baldonnel to facilitate a logistic re-supply flight to Chad. It is possible that this aircraft was mistaken for a KC-135.
These re-supply flights would normally depart in the early morning to avoid potential Air Traffic Control congestion over Europe during the day and I have also been informed that the criss-cross patterns referred to are most likely caused by high altitude commercial aircraft that cross over Ireland early in the morning en-route from the US to European destinations. These ‘contrails' are not produced by low altitude aircraft.