On 6 February 2019, an Airbus A330-200 Captain’s Audio Control Panel (ACP) malfunctioned and began to emit smoke and electrical fumes after coffee was spilt on it. Subsequently, the right side ACP also failed, becoming hot enough to begin melting its plastic. Given the consequent significant communications difficulties, a turnback to Shannon was with both pilots taking turns to go on oxygen. The Investigation found that flight deck drinks were routinely served in unlidded cups with the cup size in use incompatible with the available cup holders. Pending provision of suitably-sized cups, the operator decided to begin providing cup lids.