AS ANYONE who flies is aware, the airlines are putting more and more seats into their planes to make the flights more profitable. Some time ago I wrote about a human engineer who was assigned to devise ways of packing as many people into a plane as humanly possible.

He was the first one to recommend putting seats in the luggage racks, and also tearing out lavatories to make more room for paying customers.

He also wanted to sell eight seats in the cockpit but the Airline Pilot's Association protested, and it was temporarily put on the back burner.

I met him on the shuttle flying from Washington to New York the other day. We were seated next to each other -- our knees scrunched up to our chests and our shoulder blades sharply pressed into each other.

"You've done a marvelous job," I told him. "Who would ever have thought you could have doubled the number of human bodies aboard an airplane in such a short time."

He was observing everything going on, and finally said. "I've been hired to figure out how to get 30 more seats in."

"It's impossible," I said. "Unless you use the aisle."

"I can't use the aisle," he told me in disgust. "The CAB has some damn-fool regulation that you can't put seats in the aisle. The government is strangling the aviation business."

"Everyone seems as packed in as possible," I told him. "I guess you'll have to recommend them flying bigger airplanes."

"I'm not being paid for that," he said. "My job is to get more seats on the planes the airlines already own."

"What about the freight compartment below?" I asked.

"I thought of that. But we can get only 12 seats in there and people might complain if their bags didn't arrive on the same plane as they did."

"I guess there's nothing you can do except make the people smaller."

He didn't realize that I was making a joke. "We've been working on that, but the few people we tried our machine on squawked so much, we gave it up."

"Well, you can't win them all," I said. The human engineer was staring out the window. Suddenly his eyes widened. "Do you see what I see?"

"What's that?"

"The wing of the airplane."

"Of course I see the wing of the airplane."

"It looks pretty solid, doesn't it?"

"I hope so," I said. "Wait a minute -- you're not thinking what I think you're thinking."

"Why not?" he said excitedly. "You could bolt in 15 seats on each wing and who would know the difference?"

"But wouldn't it be windy out there?"

"You'd put the seats facing the back so the people would be looking at the tail of the plane. On a clear day, the passengers would get a fantastic view of New Jersey."

"Are you sure people would agree to fly from Washington to New York on the wing of an airplane?"

He was writing furiously. "We'll give them 20 percent off on their no-frills tickets. Thirty percent if they fly as a family."

"I'm not certain you'll get many takers," I said skeptically. "The inside of the plane doesn't look like 'Love Boat,' but at least we don't have to worry about the wind-chill factor."

"Look, years ago you would have screamed murder if you had to fly with your knees on your chest. Now you accept it without a murmer. When you buy an airline ticket, all we promise to do is get you there. There is nothing in the contract which gurantees where you'll sit."