 In preparation for the 2017–18 season, Alt was among the last cuts at the Flyers training camp and was familiarly assigned to Lehigh Valley.As the Phantoms best defenseman to start the year, Alt returned to the NHL for the first time in three seasons, as he was again used on an emergency basis in a 4-3 overtime defeat to the Arizona Coyotes on October 31, 2017.He was later officially recalled and featured in 7 more games before he was returned to the Phantoms on December 30, 2017.