Replies to recent columns:

BANNING SMOKING ON PLANES--"I wish it were that simple," writes John J. Carroll of Arlington. "The problem as I understand it is that most aircraft fires start in the lavatory -- and where do you suppose the secret smokers would do their dirty deed?"

Good point, John. But wouldn't a smoke detector mounted on the bathroom wall provide sufficient protection? And if you want to be extra safe, why not put ashtrays on the bathroom counter, right beside the sink, where no one could miss them? That way, a smoker sneaking a drag or two would be far less likely to dump ashes or butts in the toilet or the trash--the two places where a fire is most likely to start and difficult to extinguish.

DISCARDING NEWSPAPERS ON THE SUBWAY--Permit this, and our subway becomes as grubby as New York's, I argued. But Philip Simon of Northwest says that a left-behind paper can be a "desirable embellishment to the trains."

"I have noticed that when an arriving train car has a few abandoned newspapers, the boarding passengers tend to choose the seats beside the papers," Philip says. "Personally, I make a special effort to find a paper if I'm not already carrying one . . . .

"This communal newspaper sharing has many desirable aspects. It increases information flow. It generates more complete and efficient use of a social resource--the newspaper. It engenders a spirit of community. It creates a feeling of transfer between strangers in a commuting society. In fact, it has many of the positive aspects of a library."

I dare Philip to find me a library where real estate ads are scattered over 25 square yards of floor and drug store supplements are trampled into purple and green confetti. Still, he's on the right track. Perhaps the way to assure the communal spirit Philip says he sees is for us to allow newspapers to be left behind on subways--but to provide racks where leave-behinders can put them.

GRAMMAR ATOP THE EXPRESS LANES--Yippee, said I, when Safeway opened a store recently with signs reading: "Nine Items or Fewer" posted above the speediest checkout lines.

Humbug, says Joyce Elaine Tarpley of Rockville.

"I can count on one hand the number of times I have ever been in an express lane that lived up to its name," says Joyce. " . . . It does not matter in the slightest whether the sign reads 'Nine Items or Less' or 'Nine Items or Fewer' because there's always going to be some turkey in line with 42 items in his or her basket!"

Sad but true, Joyce. But wouldn't you rather be surrounded by correct English while gnashing your teeth? I sure would. Don't make me look at "Less" at the same time Turkey is piously explaining to the clerk that he didn't see the sign. That would be one too many for what's left of my stomach lining.

DEALING WITH OBSCENE PHONE CALLS--I advised a reader who'd been victimized by a heavy breather to change her number or temporarily disconnect her phone. But a number of others filed additional suggestions.

"Buy a sports whistle and blow it in the ear of the caller," says Jeanetta M. Wright of Northwest. "I tried this and it worked!"

"Get a phone with a hold button," suggests Conchita Rivera of Arlington. "As soon as he calls, just put him on hold. I did it four times and my caller went away forever. I figured if the hold button drives people nuts in offices, why not use proven methods on obscene callers?"

"Start screaming--big, loud, bloodcurdling screams," suggests Nina Van Allen of Southwest. "Now, I admit this may not be the best thing to do if you live in a big high-rise apartment. But I don't, and it worked for me. The guy who called me stopped right in the middle of a sentence and said, 'Wow, lady, you must be really crazy.' Then he hung up and never called back."

"Contact the phone company," suggests Harold Smith, who did just that after his daughter began getting calls at all hours. "They'll put a tracing device on your phone. All you do is make a note of the date and time you received the obscene calls. You do it for 30 days. Then they take care of it."