American Airlines cancelled a flight from Detroit to Philadelphia after a co-pilot was suspected of being intoxicated.
The pilot, who hasn’t been named, allegedly tested above the legal limit for blood alcohol content, according to a statement issued by the Federal Aviation Administration.
Officials had reported his behaviour.
The pilot was detained at a security checkpoint at Detroit Metropolitan Wayne County Airport in suburban Romulus, Michigan.
“Flight 736 was cancelled and we are re-accommodating our customers on other flights,” American Airlines spokeswoman Laura Nedbal said.
“This is a serious matter and we are assisting local law enforcement and the Federal Aviation Administration with the investigation.”
She declined to say what range of penalties a pilot could face if found to be unfit for flight due to intoxication.
Several college students who were on spring break tweeted about the incident, which left them stranded at the airport.
FAA rules concerning pilots and alcohol are stricter than those enforced for motorists.
The agency prohibits pilots from flying while under the influence of alcohol, specifically when their blood alcohol content is 0.04 percent or higher, or within eight hours of consuming any alcoholic beverages.
The American pilot allegedly tested above the 0.04-percent level.
The pilot was scheduled to fly on an Embraer E-190 – smaller than an aircraft such as a Boeing 737 but larger than a typical regional jet.