The scene was the security checkpoint near the Piedmont Airlines gates at Baltimore- Washington International Airport. David Thompson was about to board a flight to Detroit with his 3-year-old daughter Kelly. As he does every time she flies with him, David had just bought Kelly a purple helium-filled balloon with which to amuse herself during the trip.

But the security guard didn't find the balloon amusing. He took it away from Kelly, without asking, and announced that Piedmont doesn't allow helium-filled balloons aboard its flights.

David asked to speak to a supervisor. Eleanor Williams appeared. She repeated what the security guard had said. Then she ordered David to take the balloon outside the airport terminal altogether, "so that people could breathe."

When David termed that demand "idiotic" and ignored it, Eleanor called a state police officer.

Fortunately, the situation didn't get any uglier. The Piedmont flight was canceled, so Kelly got her balloon back. But Piedmont got a letter from David (copy to me) that would blister your socks.

I never would have guessed this before I started looking into the incident, but Piedmont had good reason for banning Kelly's balloon.

A helium-filled balloon may seem innocent. But it is "a hazardous material," said Glen Hilburg, cargo manager for Piedmont at BWI. "It is combustible, like an oxygen tank, and therefore it's restricted material. All airlines participate in this regulation."

Bob Bennington, Piedmont's station manager at BWI, said that "this isn't the first time that's ever happened. Helium is nonflammable and all nonflammable gas is not permitted. Most people do not understand that."

Joann Sloan, a public relations representative for the Federal Aviation Administration, said airlines may fear that a child's balloon is filled with nitrogen (which is flammable) rather than helium. "If it was helium, there shouldn't be a problem, but I guess they don't want to take a chance," Joann said.

A spokesman for the Air Transport Association guessed that airlines bar helium-filled balloons because the balloons may expand and burst as planes climb to higher altitudes. "Airlines might worry that it would startle someone," the spokesman said.

What's puzzling in this story is how David and Kelly got away with taking helium-filled balloons aboard planes in the past. Probably gate agents didn't want to disappoint a cute little girl, and just looked the other way.

But the most puzzling part of the story is why the Piedmont staffers at BWI were so imperious and nasty to the Thompsons.

There was an easy compromise available: Let Kelly hold onto her balloon while she was in the gate area, but take it away once she got on the plane. Instead, the Piedmont staff handled the situation with all the finesse of a Marine drill sergeant.

David Thompson was basically wrong about the BWI incident, at least as far as security considerations are concerned. But he is as right as can be about the question of courtesy. Didn't the Thompsons deserve more of that? Or has courtesy gone up, up and away in the world of today's airlines?

Speaking of gaffes by airline personnel, I witnessed a beauty last month.

On a breakfast flight to Atlanta aboard Eastern Airlines, the steward served me my rubber french toast (in the window seat). Then he served my wife hers (in the middle seat). Then he eyed the man in the aisle seat, who was snoozing like a kitten.

"Are you sound asleep?" the steward asked the man, perhaps three inches from his ear.

Not any more, he wasn't.

And while we're pointing out the rigors of travel, let's give Alice K. Reinders of Arlington a minute on the soapbox.

Alice is married to a man who is 6-feet-4. All of their children are between 6-feet-4 and 6-feet-9. You would think that the motel industry would have had customers in the past who are that tall -- and taller.

But as Alice points out, beds in motels are always made to accommodate people who are six feet tall or less. So whenever the Reinders family stays in a motel, they must kill 10 minutes remaking every bed in sight.

I checked with some of the national motel chains. They say that most of their beds are only seven feet long. They point out that it would be awfully difficult to make someone 6-feet-9 feel comfortable in a bed that's only three inches longer than he is. They also point out that to make a bed more loosely might suggest that the bed hadn't been made since the last customer slept in it.

My solution: Can't motels keep extra-long beds on hand, so they can be wheeled in when the Reinders family (or any basketball team) wants to spend the night?