May 5, 2007  -- A California man may pay with prison time for a public display of affection on a plane.

Carl Persing was convicted Thursday of interfering with flight attendants and crew members after he and his girlfriend, Dawn Sewell, were seen "embracing, kissing and acting in a manner that made other passengers uncomfortable," according to a criminal complaint.

According to assistant U.S. Attorney John Bowler, Persing will likely serve jail time for the federal felony conviction, the Associated Press reports. He was convicted after a three-day trial in U.S. District Court in Wilmington, Va.

According to an FBI indictment, Persing's face was pressed to Sewell's vaginal area during the September Southwest Airlines flight from Los Angeles to Raleigh, N.C. When a flight attendant gave them a second warning, Persing reacted angrily and the couple, both in their early 40s, were arrested when the plane reached its destination.

At the time, the couple's lawyer claimed that Persing had his head in Sewell's lap because he wasn't feeling well and that the flight attendant had humiliated and harassed them.

Persing's conviction is the latest example of how in the wake of 9/11 and new security regulations, many airlines have become increasingly vigilant -- perhaps even uptight -- about minor infractions. And many passengers realize they need to be on their best behavior when they take a flight.

"As a potential act of terrorism, it's being a little oversensitive," Charles Slepian, an aviation security expert at the Foreseeable Risk Analysis Center, said about Persing's case. "After all, the mile-high club has been around for at least 50 years. But flight crews are sensitive that some passengers get upset when others get cozy, and that could erupt into an altercation."

Although it usually covers serious criminal activity, the Patriot Act can apply to minor infractions on flights.

"You can't make any threatening gesture to an attendant because it does violate the Patriot Act," explained Slepian. "They don't want you getting out of your seat except to go the lavatory. The whole idea is to keep control. If you react to the attendant, you're going to get locked up."

Flight attendants, with their increased power, definitely seem to be getting more sensitive to all types of behavior. Emily Gillette claims that she was kicked off a plane last month for nursing her baby on a flight between Burlington, Vt., and New York City. A spokesman for Freedom Airlines, which was operating the Delta commuter flight, says that Gillette was ejected because she declined an attendant's offer of a blanket.

One passenger on a Delta flight from Los Angeles to Salt Lake City was arrested for leaving his seat to go to the lavatory less than 30 minutes before landing (due to the incident, air marshals ordered all passengers to put their hands on their heads for the rest of the flight). And an Orthodox Jewish man was kicked off an Air Canada flight for praying, which attendants claim was making other passengers nervous.

Other passengers have been taken off flights for making jokes, such as asking attendants if they had "checked the crew for sobriety" and "where do you keep the bomb?" Some have been booted for taking onboard hand cream, matches and bottles of water, and for sniffing something in a bag.

And there doesn't seem to be an age limit for the violators. In 2005, a United Airlines flight out of Chicago was delayed because a small boy said something inappropriate.

"It seems like there's a real increase in these types of incidents. They're more sensitive to minor infractions," said Anne Banas, the executive editor of SmarterTravel.com. "There's a no-tolerance policy. It really seems like you have to be on your best behavior on the plane."

So, what else constitutes bad behavior? According to Banas, try to avoid the following when flying: making jokes about blowing up planes; getting drunk; bumping other passengers with big bags; taking up all the space in the overhead compartments. Banas advised that you should show respect other passengers by not cursing and shouting.

The irony is that many travelers are already following those rules. While flight crews may seem less tolerant of questionable behavior, passengers are actually getting nicer to the attendants, by at least one important measure. The number of unruly passengers who have been penalized by the Federal Aviation Administration for trying to "assault, threaten, intimidate or interfere with a crewmember" has dropped dramatically in the last two years and is on track to hit a record low. In 2004, the FAA recorded 304 enforcement actions. Through September of 2006, there were only 79 such actions.

Of course, in these very sensitive times, almost everyone who flies experiences some tension, and sometimes it does boil over. In September, Seth Stein, a London interior designer returning from his vacation in Turks and Caicos, was put in a chokehold and physically pinned to his seat by another passenger on an American Airlines flight. Stein's crime: He used an iPod, went to the lavatory and his tan made him appear "Arab."

Reporting contributed by Marcus Baram and The Associated Press