Why Nail Polish and Airplanes Don't Mix

— -- When faced with several hours spent twiddling their thumbs on a flight, some travelers figure, "Why not paint them, instead?" But in-flight manicures are rarely indulged by cabin crews and the activity even led to a California woman being arrested at her destination two years ago.

So is using nail polish at 30,000 feet illegal? The short answer is no. But the practice is openly discouraged by most major airlines.

"United doesn’t have a formal policy on nail polishing in flight, but as a courtesy we may ask customers to refrain from doing so for the comfort of their fellow passengers," Karen May, a spokeswoman for United Airlines, told ABC News.

Virgin America also cited "comfort" as its reason for recommending against applying top coats in flight.

"While we don’t currently have an official policy against nail polish, as a courtesy, we do request that guests refrain from using it onboard flights for the comfort of their fellow travelers," said a spokesman for Virgin America.

The same went for Southwest Airlines.

"For the comfort of all our passengers on board, this practice is frowned upon and the customer will be asked to put away their polish," said Dan Landson, a representative for Southwest, which was involved in a paint-related police report in 2012.

At the time, a Burbank woman en route to Houston, Texas, repeatedly tried to paint her nails during a flight in spite of being asked to stop. The issue escalated between herself and two Southwest Airlines flight attendants and by the time the jet landed, airport police were waiting to cuff the passenger.

She spent 10 hours in jail for using abusive profane language, though the charges were later dropped by the DA. This event may have caused some confusion within the airline community.

Recently, another flier queried a Travel Skills Q&A column on the legality of in-flight manicures, as she had allegedly been told by a scolding flight attendant that applying polish was against the law.

But again, it is not. It's simply prohibited.

"The use of nail polish is not allowed on American Airlines flights," according to a spokesman.

With its flammable ingredients, noxious fumes and potential to stain others, its no wonder why nail polish is such a contentious carry-on item.

Still, sometimes the desire to lacquer up on long hauls supersedes social mores.

"I confess I did it once," admitted a longtime traveler who preferred to remain anonymous. "I was such a rube -- I didn't even consider why it was a problem, until the flight attendant came over and told me to shut it down."