A pilot on a British Airways flight who was suspected of being drunk was arrested at Gatwick Airport on Thursday evening.
Police said they received a call at 8.25pm on Thursday regarding "a member of airline staff suspected to have been under the influence of alcohol".
The flight, from Gatwick to Mauritius, was scheduled to leave at 8.20pm on Thursday, but the plane was left waiting at the gate while airline staff looked for a third pilot.
A 49-year-old man was arrested on suspicion of performing an aviation function while his alcohol level was over the prescribed limit, police said.
He was taken into custody and later released under investigation.
British Airways said it was taking the matter "extremely seriously".
"We are sorry for the delay to our customers," said a spokesperson. "The aircraft remained at the gate until an alternative third pilot joined the crew.
"The safety and security of our customers and crew is always our top priority."
The airline added that it is assisting police with inquiries.