A court in Belfast has granted an extension to the detention of the suspect until 10 pm on Thursday, March 2.
Earlier a court granted an extension to the detention of a 71-year-old man until 10pm on Wednesday, 1st March.
Both men remain in custody in the Serious Crime Suite at Musgrave Police Station.
Four other men arrested, aged 22, 38, 43 and 45 have been released following questioning, the investigation continues.
DCI Caldwell remains in a critical and sedated condition in Altnagelvin Hospital in Derry.
Two masked gunman fired up to ten shots at the senior MIT detective after he had just finished a junior football coaching session.
Major Investigation Team detectives continue to ask for the public’s help and would appeal to witnesses or those with information to get in touch by calling 101.
Detectives are also highlighting a reward of up to £20,000 from Crimestoppers, who are a charity and independent of the police.
The reward is offered for information given directly to Crimestoppers that leads to the arrest and conviction of those responsible for DCI Caldwell’s attempted murder.
Contact the charity anonymously on 0800 555 111 or online at www.crimestoppers-uk.org
Information, including photos, CCTV and dash-cam footage, can also be provided to police through the Major Incident Public Portal at https://mipp.police.uk/operation/PSNI23S03-PO1Tags: