Two hours after his arrest, police determined Gronych's blood alcohol content (BAC) was more than three times the legal limit.
"We tested him approximately two hours after we took him into custody and he still blew at that extreme level," Stacey said. "I can't tell you when he had his last drink, but he was pretty high."
He faces charges of having control of an aircraft while impaired and having care and control of an aircraft while his BAC exceeded .08.
Gronych is from Slovakia and was in Canada on a work visa, Stacey said. Police did not know of any previous incidents involving the pilot.
Transport Canada is also investigating the case. Authorities expect the governmental agency to levy additional charges against Gronych.
"He won't be flying anytime soon," Stacey said.
In a statement released to CBC News, a Sunwing spokeswoman apologized for the incident and called it a "very unfortunate matter."
"We are very apologetic for any upset that this has caused and would like to assure our customers that safety remains our utmost priority," spokeswoman Jacqueline Grossman told the news network in an email.
Saturday's flight had planned stops in Regina and Winnipeg before it skipped over America and continued on to Cancun, police said. The flight left with another pilot.
Sunwing Airlines is a low-cost airline based in Toronto.