I was thinking about my friend Jen the other day. I was feeling sorry for her. Jen is reaching the end of her 30s. She’s childless, and not by choice. I know that, on some very deep and ancient level, this hurts her. I can see it in the way she looks at mothers with babies, and in the way she quickly volunteers to help out with her friends’ children. She babysits. She takes them on excursions to museums and parks. She dotes. Because she can, because the parents welcome the extra love and attention offered to their kids, and I guess because biology wants her to mother.

When I listen to Jen talk about her wishes for children, I can almost feel the ache. It must be very difficult to be a childless woman.

Jen tried with her first husband, without success. Last year she briefly considered attempting to conceive with the help of a friend, and raising a child on her own. Then she was pulled into a whirlwind romance, followed quickly by a second marriage. The marriage is going well, with love aplenty, but thus far conception has remained frustratingly out of reach.

I was thinking about Jen because my new friend Tanner had just thrown up on my second-best suit.

My frame was squeezed into a window seat near the back of a plane from Houston to Atlanta. At the front of the plane, businesspeople like me were stretched out drinking free cocktails and reading the paper. Flying last-minute, I’d taken what I could get, not without a little grumbling to myself.

Now I was wiping unpleasantness off my arm, while my seatmate apologized.

“Oh, damn. I’m sorry about that,” said Mel, handing me more baby wipes from a well-stocked bag between her feet.

“And well you should be, Mel,” I told the young woman beside me. “I’m simply shocked that Tanner would spit up on me while I’m burping him. Obviously, you’re raising him wrong.”

Mel grinned, and I sat the eight month-old on my knees, holding him with my left hand and wiping with my right.

“Do you want me to take him back now?” she asked, taking the baby blanket off my shoulder.

“Let’s see what Tanner says,” I replied. I turned him around to face me. What a funny looking little thing. Pudgy face with brown eyes seeking out my own. Tiny, pudgy hands gripping my index fingers. He uttered a good-natured gurgle.

“I don’t know, Mel,” I said. “I think he wants to visit awhile longer.” The flight was smooth for most passengers, but not for Tanner. He bounced up and down on my knee over two states.

Even if you're a bachelor like me, if you travel a lot, you learn to feel for women flying alone with babies. In the age of unhappy travel, in a cramped cabin full of unhappy travelers, a baby is about as welcome as Donald Trump at an Occupy rally. The mothers, with their strollers and baby bags full of snacks and toys and supplies, manage the challenges and awkwardness with an aplomb only a mother can muster.

While Mel talked about meeting her husband at his parents’ home in Florida, and the fun they had planned, I made silly noises and stroked Tanners impossibly soft cheek with the backs of my fingers. It occurred to me how very much my friend Jen would give to have her own child like little Tanner, to touch and teach and hold and worry about. I thought about how well she knew what she was missing, and how much she wanted it.

In Atlanta, Mel and I waited for the stroller. The descent to landing, with the cabin pressure increasing, had hurt Tanner’s ears. He’d cried a bit until he began to suck on his bottle, the swallowing effectively equalizing the pressure. Now he was asleep on my shoulder. When the stroller arrived, I carried the tiny boy up the Jetway and deposited him gently in his chariot.

He woke up and met my eyes once more. Mel thanked me graciously for my help on the flight. I told her it was nothing, and that Tanner was beautiful. Then Mel took Tanner’s little hand and helped him wave bye-bye to me. I waved back and stood and watched mother and son head off down the terminal.

I felt bad for my friend Jen. It must be a difficult thing to be a childless woman in her late 30s. I imagine she sometimes feels a certain sadness, and a little ache somewhere inside. Maybe right in the pit of her stomach.

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