The co-pilot was taken into custody after allegedly failing a Breathalyzer test administered by airport police, Detroit Metropolitan Airport spokesman Michael Conway said yesterday.
As a result of the incident, American Airlines canceled Flight 736 from Detroit to Philadelphia yesterday.
"We are re-accommodating our customers on other flights," American Airlines spokeswoman Laura Nedbal said in a statement.
"Safety is our highest priority and we apologise to our customers for the disruption to their travel plans."
The co-pilot was administered a more precise sobriety test at a local police department. Both tests showed he was over the legal limit for operating an aircraft, CNN quoted the airport police as saying.
Authorities did not name the co-pilot pending possible charges, but said he was born in 1965 and is a resident of Pennsylvania.
He was later released from custody after his alcohol level dropped, Conway said.
Airport police are now developing a case to present to the local prosecutor's office, Conway said, noting that these kinds of incidents are "extremely rare.
