The Manchester Arena bomber Hashem Abedi and the Parsons Green bomber Ahmed Hassan have both refused to attend court after being charged with attacking a prison officer.
They are accused of assaulting Paul Edwards on 11 May at Belmarsh Prison.
He suffered a cut to the head, bruising and hearing problems, Westminster Magistrates' Court heard.
Abedi and Ahmed, who are both being held at Frankland Prison, refused to attend the videolink room for the case.
Their hearings have been relisted for Thursday.
A third convicted terrorist, 23-year-old Muhammed Saeed, appeared by videolink from HMP Whitemoor.
He indicated a not guilty plea to the alleged assault and will next appear at Woolwich Crown Court on 5 May.