Pilots cannot have a blood or breath alcohol concentration of .04 or more. (Representational)

In the span of less than a week recently, authorities arrested three pilots from two different airlines under suspicion of intoxication before they were about to fly.

But despite the widespread coverage of the pair of incidents in late July and early August, authorities say it's highly unusual to find an intoxicated pilot. Between 2010 and 2018, nearly 117,000 U.S. pilots were tested for alcohol, according to the Federal Aviation Administration. Of those, 99 were found above the legal limit. When those violations are discovered, the consequences can be severe.

"It's because of the seriousness with which the authorities take the safety of air travel," says Chris Smith, partner at the Air Law Firm in London.

In a safety brochure that calls alcohol and flying "a deadly combination," the FAA cautions: "Any factor that impairs the pilot's ability to perform the required tasks during the operation of an aircraft is an invitation for disaster."

Federal Aviation Administration regulations say a pilot cannot have a blood or breath alcohol concentration of .04 or more, which is half the legal limit for driving in the United States. And pilots are not allowed to drink any alcohol within eight hours of acting or attempting to act as a crew member - "from bottle to throttle," as the FAA says.

The agency says that the rules are a minimum and suggests a more conservative approach of staying away from booze for a full 24 hours before a flight.

"Ideally, total avoidance of alcohol should be a key element observed by every pilot in planning or accomplishing a flight," the FAA says in the safety brochure. It warns that a hangover can be just as dangerous for a pilot as intoxication.

Pilots can be criminally charged even if they haven't taken off in an aircraft, as well as face action from the FAA and their employer.

"If you get arrested for flying while intoxicated ... the FAA and airline's going to move in so quickly to revoke the privileges," says Doug Murphy, a Houston defense attorney who specializes in driving while intoxicated cases. "It won't be an automatic revocation, but there will be a suspension that will prevent them from flying until they've made a determination and figured out what the facts are."

He added: "In most of those cases, they're done."

Airlines are required by the FAA to randomly test pilots for drugs and alcohol, and tests can also be required after an accident or when someone - fellow crew, security personnel, or other - has reason to suspect a pilot might be under the influence.

That was the case in both of the recent incidents. On July 30, 37-year-old Delta pilot Gabriel Schroeder was arrested in Minnesota a little after 11 a.m. after he was found with an alcoholic container and suspected of being impaired, according to arrest data from the Minneapolis-St. Paul International Airport's police department. Authorities became suspicious, the report said, when he left a crew member security line after realizing that additional screening was ahead. The scheduled flight to San Diego was delayed an hour to wait for someone to replace Schroeder.

Just a few days later, on the morning of Aug. 3, two United pilots were taken into custody in Glasgow, Scotland after being suspected of intoxication. Their flight to Newark was canceled. One was released without being charged and the other, 61-year-old Glendon Gulliver, was formally charged with being over the alcohol limit as he was preparing to fly, according to The Associated Press.

In both cases, the pilots have been removed from flying pending the outcome of the investigations, the carriers said.

"Delta's alcohol policy is among the strictest in the industry and we have no tolerance for violation," the airline said in a statement. "Delta is cooperating with local authorities in their investigation."

Some countries have more stringent rules than the U.S., and pilots would be subject to them under local jurisdiction as well as FAA regulations; Scotland, for example, has a lower threshold for alcohol concentration than the United States. And airlines' policies might be even more strict than the FAA. A United spokesman said this week that the carrier is changing its rules to require pilots to avoid drinking for 12 hours before a flight, rather than eight, in the coming days.

Over the past couple of years, three global high-profile cases of flying while intoxicated, or preparing to fly, resulted in prison sentences of eight months, 10 months and a year.

Even a conviction for driving under the influence or revocation of a drivers license because of the offense must be reported to the FAA, which could lead to a pilot losing the privilege to fly.

"License suspensions and convictions can really be a career-ender for a pilot and cause the revocation of their pilot's license," Murphy said.

There is a path to returning to the air, though. An FAA-run occupational substance abuse treatment program, which is supported by airlines and unions, coordinates evaluation, diagnosis and treatment of pilots who struggle with substance abuse. Through the Human Intervention Motivation Study program, pilots can work toward getting their medical certification reinstated and returning to work, the official HIMS site says.

Smith, of the Air Law Firm, says there's a big difference between someone who enters the program voluntarily because they are fighting addiction and someone who is caught working while intoxicated.

"Whether they would be reemployed certainly with the same employer, whether or not they would be successful in regaining their pilot's license again would be a matter for the regulator," he says. "But I would suspect that ... self-referring would be a strong mitigating factor that the authorities would consider."

Despite the out-sized attention that such cases get, the Flight Safety Foundation, an organization dedicated to aviation safety, doesn't consider the issue of drunk pilots a "significant safety concern."

"There are good counter-measures already in place that are pretty effective," says Mark Millam, vice president of technical programs. "And the chances of somebody actually getting on the airplane are pretty darn slim."