An American pilot has admitted preparing to fly a passenger jet from Scotland to the US while more than twice the drink-fly limit.

Paul Grebenc, 35, was first officer on a United Airlines flight from Glasgow Airport to Newark, New Jersey, on August 27 last year when concerns were raised about his fitness to fly.

A blood test later found he had 42 microgrammes of alcohol in 100 millilitres of blood, more than twice the legal limit of 20mcg.

Grebenc, a former US Air Force pilot who is still a reservist, pleaded guilty at Paisley Sheriff Court on Thursday.

The court heard that on the morning of August 27, Grebenc and his United Airlines colleagues were brought to Glasgow Airport from the Hilton Hotel in Glasgow, where they had spent the night, having flown in from the US the previous day.

They were due to fly a Boeing 757 to Newark at 9am. But as they passed through the staff search area, security staff smelled alcohol on the breath of the other first officer, Carlos Licona, and raised the alarm.

Police were contacted and went to the departure gate, where Licona and Grebenc were removed from the flight.

Fiscal Depute Scot Dignan said: "Police did not go on board the aircraft as they wanted to be discreet and not alarm passengers. Grebenc was asked to disembark with Licona as police also had suspicions regarding him.

"He was taken to a quieter spot. At about 9.30am he was asked to provide a specimen of breath for analysis which proved positive and he was taken in a marked police vehicle to Govan police station."

Later that day, he provided a blood sample , which showed he was more than twice the legal limit.

Licona was sentenced to ten months in prison earlier this month after he admitted boarding a flight while under the influence of alcohol.

The plane took off later that day with a new crew and 141 passengers on board.

David McKie, defending Grebenc, said his client was extremely remorseful.

He said: "He has asked me to express his remorse and apologises to the court and passengers for his irresponsibility and what was a significant misjudgment on his part. He takes full responsibility for his actions."

Mr McKie told that court Grebenc flew refuelling aircraft for the US Air Force in war zones such as Iraq and Afghanistan, including mid-air fuel transfers.

Alongside his commercial work with United Airlines, he still serves as a reservist with the USAF and has been involved in training young pilots.

His wife is also a USAF pilot and the couple, who live on an air base in Mississippi, have two children aged two and four.

In mitigation, Mr McKie said at the time of the incident Grebenc had been in an argument with family and was waiting for a prognosis after a shadow had been found on his son's lung which doctors feared might be cancerous.

He said: "He recognises that he ought to have stopped drinking at an earlier point that evening and his failure to do so will have catastrophic consequences for him, his career and for his family."

He said his client has been placed on the HIMS (Human Intervention Motivation Study) rehab programme by his employers in conjunction with the federal aviation authority.

Grebenc is due to be sentenced later.