An American Airlines pilot was arrested in front of passengers on Saturday after he allegedly failed a breathalyzer test at the Detroit Metropolitan Airport.

The unidentified co-pilot forced the cancellation of Flight 736 shortly before it was set to take off for Philadelphia, a spokeswoman told TIME on Sunday. The pilot had failed two sobriety tests after a transportation security agent saw him acting suspiciously, and his blood alcohol content was over the legal limit, Detroit Metropolitan Airport spokesman Michael Conway told ABC affiliate WXYZ.

“This is a serious matter and we are assisting local law enforcement and the Federal Aviation Administration with the investigation,” American Airlines spokeswoman Laura Nedbal said. “We will handle this matter appropriately as the safety and care of our customers and employees is our highest priority.”

The airline did not release additional information about the pilot.

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