Fellow Flyers Make Fast Friends At 40,000 Feet

He was 10 years old and 5 feet 2 inches tall already. ''I'm the tallest boy in my school,'' he told me proudly.

She was 11-1/2 years old and petite, with long brown hair and a great new backpack purse that she had received from her mother for Christmas.

They were both comparing their brand new San Francisco 49ers starter jackets, and they were having a wonderful time, even though they'd never seen each other before the stewardess sat them together on the crowded plane. When the peanuts came and the drink orders were taken, they both ordered the same kind of soda.

I was their seatmate on a sold-out plane, traveling between Christmas and New Year's Day.

When I first sat down I assumed they were brother and sister and their parents were seated with other siblings in a nearby row. But they proudly told me that they were traveling alone.

''Every time I travel alone, they sit me next to someone else who's traveling alone,'' the boy said in mock disgust. ''And look who I had to get this time!'' he said.

She socked him on the arm in protest; he returned the affectionate blow; and they laughed joyously together as if they'd each found their one true love.

They were wearing these pin-on buttons with attached identification papers of some kind and they had been told not to take these buttons off for any reason until the authorized person meeting them at the other end of the trip had signed for and claimed them.

''We hate these things,'' said the little girl. ''Anyone who is under 12 has to wear them,'' she added.

I saw them after the plane had landed, with the stewardess and the authorized people picking them up, getting the required signatures.

For the whole trip, I felt as if I was listening in on a private line.

She was ''going out'' with a sixth grader.

He had a girlfriend named Jennifer, and he illogically wondered if his new-found friend had ever met her. ''Everyone knows Jennifer!'' he said.

They knew some rap lyrics and this hand-jive stuff that they did over and over as if they had been practicing together for months.

They laughed and fought and called each other names and talked about their families, their friends, and their schools. They were as comfortable with each other as two old friends, even though they had just met.

''Hey! Know what a two-two is?'' the girl asked the boy.

''What's a two-two?'' he said.

''I'm a two-two, and you're a two-two,'' she said. ''You know. You have two homes and two sets of parents, and so do I. We're both two-twos,'' she exclaimed delightedly.

They laughed over this and then started a wild back-and-forth banter: ''My Dad does this....''

''Well, my Mom does that....''

''Well, my stepdad is this...''

''And my stepmom does this....'' And so on until they ran that whole topic into the ground.

Then they started talking about where they had traveled and where they had lived:

''I've been to Paris....''

''Well, I lived in Germany....''

''Well, I was born in Dallas....''

''I lived in California....''

''I lived in Missouri....''

''Well, I've been to Chicago.''

''Well, so have I!''

A small crisis occurred when the boy got chilly and put on his starter jacket. In the process he knocked off the button, and his identification papers fell to the floor. He and the girl scrambled around to find everything and get it all reattached to his shirt. He was genuinely worried that he had broken a very important rule.

''It was only off for a little bit,'' he said apologetically to me, as I was the only grown-up who had witnessed the accident.

I looked at the girl, who was looking at me to see what I would do. I took on the countenance of a judge. ''As long as it was only off for a minute,'' I said with mock authority, ''and it's back where it's supposed to be....''

I paused, and he patted the button on his chest as if to confirm that this was true. ''I don't think we have to tell anyone,'' I said.

He looked relieved, and we all smiled at one another. Then they went on to something else, and I pretended to take a nap.

There were probably lots of two-twos traveling across the country over the recent holidays, but I'll bet that none of them had as much fun as these so-grown-up, so-innocent, so-delightful two.