When a coach passenger attempted to use the first-class bathroom during a June 28 Delta Air Lines flight — against the flight attendant's warnings — police were on hand to investigate when the plane touched down at Lambert-St. Louis International Airport.

When a 46-year-old Ballwin man ignored requests to hang up his cellphone on a United Airlines flight last year, he, too, was referred to authorities.

And when a Florida man threw a bag of peanuts — apparently in disgust — and cursed at flight attendants on board a Dec. 6 Southwest Airlines flight, police quizzed him about it when the plane reached St. Louis.

While the Federal Aviation Administration shows the number of enforcement actions against disruptive passengers has tapered off since reaching a 10-year high in 2004, flight crews and others say the skies can still be an unfriendly place when dealing with stressed-out air travelers.

"Flight attendants often see spikes in unruly behavior when there is a new policy implementation," said Corey Caldwell of the Association of Flight Attendants.

For instance, when airlines began charging passengers for checked bags, Caldwell said, there were more "incidents" in airline cabins. There was a spike in frustrated fliers after the Transportation Security Administration required travelers to keep gels and liquids in their checked luggage.

It is against federal rules to do something that impedes with an airline flight crew. Specifically, those rules state that "no person may assault, threaten, intimidate, or interfere with" crew members in performance of their duties.

In 2005, the FAA reported 304 enforcement actions against "unruly passengers" under those regulations. The numbers have been dropping steadily since then — to 121 in 2010 — but Caldwell and others say those numbers don't tell the whole story.

"Those are the most extreme cases," she said.

Violations range from failure to turn off a personal electronic device when asked to do so to actual assault on a crew member.

Lambert airport Director Rhonda Hamm-Niebruegge, a former managing director for American Airlines in St. Louis, said only a small percentage of the interference incidents are actually prosecuted.

"Very, very few escalate to where you've got the FAA or an FBI agent involved," Hamm-Niebruegge said. "That's a very small percentage. I don't know what it is, but I bet it's less than one-half of 1 percent."

During the last 14 months at Lambert, there have been at least 11 flight crew interference and peace disturbance reports taken by airport police. Many of them did not call for further action.

A notable exception occurred on a Chicago-to-Houston Continental Airlines flight on Mother's Day. The pilot had to divert to Lambert after a passenger allegedly tried to open a jet door during flight. The case is pending, and the defendant, Reynel C. Alcaide, must undergo a psychiatric evaluation.

Other unruly passengers that have been reported to Lambert police included:

• A 50-year-old Wisconsin man whose lengthy stay in the restroom of an AirTran passenger jet threatened to delay takeoff to Atlanta and led to flight attendants knocking on the door to get him to return to his seat. After spending at least 11 minutes in the restroom, according to witness accounts, the man returned to his seat — irate — and police were called to remove him from the plane.

• A West Palm Beach woman who failed to keep her dog in its kennel on a Dec. 9 American Airlines flight from Dallas to St. Louis. The woman denied she took the dog out of the kennel but acknowledged she held it on her lap — against the instruction of flight attendants.

• A 40-year-old Michigan man who appeared to be intoxicated and disturbed female passengers "by getting close to their faces while he talked," according to a police report. The man also failed to strap on his seat belt when the light was activated before the Southwest flight landed at Lambert on Feb. 9.

• A passenger on a Los Angeles-to-Chicago American Airlines flight grabbed a flight attendant's ID card from around her neck and struck her in the chest area after the plane was diverted and landed at Lambert. The passenger had asked to get off the plane and "did not like the response given by the flight attendant," according to a police report.

The airport blacked out the passenger names in police reports requested by the Post-Dispatch.

While making it clear that his organization does not condone bad behavior, Brandon Macsata of the Association for Air Passenger Rights said flying has become much less pleasant. People are being asked to pay hidden fees, and Transportation Security Administration measures have some feeling violated.

"By and large," he said, "it really stinks to fly today. It doesn't have to be that way."