The deal to bring home four Americans held in Iran almost never happened, the United States’ top negotiator told CNN on Tuesday.

In fact, it almost fell apart many times along the way – including the very night the plane was set to take off.

U.S. diplomat Brett McGurk spoke with CNN about the 14-month secret negotiations he undertook to eventually secure the release of Washington Post reporter Jason Rezaian, former Marine Amir Hekmati, pastor Saeed Abedini and Nosratollah Khosravi-Roodsari over the weekend.

Diplomats involved in the negotiations have pointed to the urgency of the Americans’ cases, including fears that Jason Rezaian faced