Concerns over Carlos Roberto Licona and Brady Grebenc’s sobriety were said to have been raised before the UA162 flight from Glasgow to Newark, New Jersey.
The flight, carrying 141 passengers, eventually took off on Saturday evening with a new crew on board.
Grebenc, 35, and Licona, 45, are both military veterans who have worked as flight instructors.
Licona was awarded in 2013 by the FFA for ‘setting a positive example’ to other pilots. Both are reservists in the Air Force.
The men were held at Goven police station and appeared at Paisley Sheriff Court on Monday morning.
They were released on police bail later the same day.
According to his LinkedIn page, Licona has spent the last 28 years working in Military Intelligence, working for the United States Air National Guard.
At the same time, the account says, he worked as a pilot, check airman and simulator instructor for Colgan Air from September 2003-January 2014. He has been working at United since then.
An Air Force spokesman confirmed that Licona is a guardsman assigned to the 111 Reconnaissance Squadron, Ellington Field, Texas, and holds the rank of senior master sgt.
In 2013, Licona was awarded with inclusion on the FAA Airmen Certification Database, according to Aviation Business Gazette.
The award recognizes ‘certified pilots who have met or exceeded the high educational, licensing and medical standards established by the FAA,’ the site said.
Grebenc is a native of Fort Worth, Colorado, living in Columbus, Mississippi.
His LinkedIn page says that he is an ‘Instructor Pilot with 8+ years of service, United States Air Force and United States Air Force Reserve.
‘Five years international fixed wing flying experience. Four years experience instructing primary flying skills in the Joint Primary Pilot Training Environment.’
In total, he says, he has logged ‘3,200+ hours of Accident and Incident-free flying in high-performance fixed-wing aircraft.’
He has been working at United since April 2015. Prior to that he had been a US Air Force T-6 instructor pilot for around five-and-a-half years, four-and-a-half of that as a reservist.
Before that, he was a KC-135 Instructor Pilot in the US Air Force for three years and eight months.
One of this Facebook photographs shows him wearing the patch of the 43rd Flying Training Squadron. A Columbus Air Force Base photograph lists his rank as captain.
Another photo on his page shows the patch of the 22d Expeditionary Air Refueling Squadron, which has been deployed in combat in the War on Terror.
A Police Scotland spokesman said: ‘Police Scotland can confirm that two men aged 35 and 45 have been arrested and are presently detained in police custody in connection with alleged offences under the Railways and Transport Safety Act 2003, Section 93.’
The section of the Act relates to carrying out pilot function or activity while exceeding the prescribed limit of alcohol.
A spokesman for Glasgow Airport added: ‘We are aware of the police incident yesterday involving two pilots.’
The incident follows the appearance in court last month of two Canadian pilots charged with being drunk as they prepared to fly a passenger jet from Scotland to Toronto.
Jean-Francois Perreault, 39, and Imran Zafar Syed, 37, were arrested on Monday July 18 before they were due to take off on the Air Transat flight from Glasgow Airport.
The men were remanded in custody when they first appeared at Paisley Sheriff Court, also charged under section 93 of the same Act.
At a second hearing at the same court they were granted bail on condition they surrender their passports.
Section 93 of the Railway and Transport Safety Act states: ‘A person commits an offence if he performs an aviation function at a time when the proportion of alcohol in his breath, blood or urine exceeds the prescribed limit, or he carries out an activity which is ancillary to an aviation function at a time when the proportion of alcohol in his breath, blood or urine exceeds the prescribed limit.’
For pilots, the limit of alcohol in the case of breath is nine micrograms of alcohol in 100 milliliters, according to the Act.
A United Airlines spokesperson refused to comment on the case, instead referring to a statement that reads: ‘The two pilots have been removed from service and their flying duties.
‘We are co-operating with the authorities and will conduct our own investigation as well. The safety of our customers and crew is our highest priority.’
An Air Force spokesperson said: ‘The Air Force Reserve Command (AFRC) holds its Citizen Airmen to the highest standards and we support any investigation of this incident by civilian authorities. ‘Any action by AFRC will be depend on the final outcome of the civilian investigation.’