Believe it or not, the answer varies depending on where your flight departs from -- and where it lands.
There are no standardized international rules on pilot alcohol consumption and testing. Instead, the International Civil Aviation Organization issues guidance and then countries set their own regulations, limits, testing regimes and punishments.
Despite being a rarity, it's an issue that has received extra attention after a series of high profile incidents. In late December, a pilot was found passed out in the cockpit before a scheduled Boeing 737 flight in Canada. In mid-2016, two pilots were arrested in Scotland on suspicion of violating alcohol rules before a flight to New Jersey.
The December arrest prompted Canada to take another look at its rules. The European Union is also considering changes.
Who gets tested and when
Alcohol testing also varies by country: India subjects pilots to a breathalyzer test before each of its 2 million annual flights, while the U.S. conducts between 11,000 to 13,000 random alcohol checks in a typical year.
The U.S. tests caught 10 pilots violating the rules in 2015.
India's stricter regulations caught 46 pilots in 2016, according to the country's Directorate General of Civil Aviation.
"If you set a zero percent tolerance limit and test everyone, you're going to have more positives," said James Stamp, global head of aviation at KPMG. "It's just a fact."
In Europe, each nation sets their own alcohol rules and then airlines develop and implement compliance procedures.
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