Former Civil Aviation Minister Praful Patel on Monday joined the Enforcement Directorate (ED) investigation in connection with the multi-crore airline slot allocation scam case.
The agency on Saturday issued summons to the former minister and asked him to appear before it on June 10 or 11.
The Nationalist Congress Party (NCP) leader was earlier summoned to appear before the economic watchdog for questioning on June 6 but he sought another date due to "prior commitments."
On March 30, the ED had filed a charge sheet against the accused corporate lobbyist Deepak Talwar in which the name of the former minister had also come up.
The agency in its charge sheet had said that Deepak Talwar, who is currently in judicial custody, allegedly acted as a middleman to favour foreign private airlines, causing huge loss to national carrier Air India.
"Talwar finalised various communications on behalf of Emirates and Air Arabia to be addressed to the then Minister of Civil Aviation Praful Patel," Special Public Prosecutor (SPP) DP Singh, appearing for the agency, had told Special CBI Judge Anuradha Shukla Bhardwaj on May 1.
Talwar was extradited from Dubai on January 30.