Lillis first took part in the Nor-Am Cup in Park City in February 2013 , finishing in 18th, 12th and eighth. He finished sixth at the 2014 Junior World Championships in Chiesa in Valmalenco and fifth at the 2015 Junior World Championships. In the 2014/15 season he took his first victory in the Nor-Am Cup in Park City and with three second and one third place, the second place in the Aerials discipline. In the following season he won the Aerials discipline of the Nor-Am Cup with three wins and two second places and also achieved third place in the overall standings. He made his World Cup debut in February 2016 at Deer Valley Resort , which he finished in ninth place. This was followed by seventh place in Moscow that same month and his first World Cup victory in Minsk . He achieved sixth place in the Aerials World Cup. In the 2018/19 season he came in three top ten placements, eighth in the Aerials World Cup. At the season highlight, the Freestyle Skiing World Championships 2019 in Park City, he jumped to seventh place in the individual and, together with Ashley Caldwell and his brother Jonathon, to sixth place in the team competition. After first place at the Nor-Am-Cup in Park City at the beginning of the 2019/20 season, he finished third at the World Cup in Minsk. In Almaty , he won his second World Cup at the end of February 2020 and thus achieved sixth place in the Aerials World Cup.
successes
World championships
Park City 2019 : 6th Aerials Team Competition, 7th Aerials Individual
United States