On a recent long-haul flight towards the back of the plane, I had just settled into my seat when two children arrived and sat beside me.

I was on the aisle in the middle configuration of four seats and the children took the middle two seats. On the other aisle was an elderly woman, who slept for most of the flight (lucky her).

The boy was about nine or 10 and the girl a couple of years older. They seemed polite and well behaved. I helped the boy with his seat belt and had a brief conversation. I assumed they were unaccompanied children, as there was no sign of parents.

But lo and behold, just before it was time to belt up and take off, the children's parents arrived from the Business Class section to check on their kids. They talked across me for a while, instructing the boy to remember to go to the toilet and telling the girl if she needed to get up, maybe she could climb over me and not disturb the elderly lady. (Thanks.) Then they sashayed back to Business Class.

The little boy was very sweet, but fidgety and didn't sleep for most of the flight. He played some game on his phone and talked at it and sang much of the time. Lovely, but a pain in the neck if you were trying to sleep. I asked him very nicely a few times not to talk, but he was too young to really understand.

At one stage, I was watching a movie that happened to have full-frontal nudity and I saw that his eyes were popping at my screen, so I fast-forwarded quickly so he wouldn't see any more of it. And I worried because he only seemed to be drinking soft drink.

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This was the point when he started to have to go to the loo frequently. I stood up for him a couple of times, but I explained he'd have to climb over me, as I would take a sleeping pill. He wasn't very co-ordinated and ended up in my lap each time, waking me up.

The parents weren't entirely MIA. They came back once or twice to check on their children and woke me up, loudly booming across me. When the mother instructed the boy to remember to go the loo, I explained I had taken a sleeping pill and suggested he use the armrests to climb over me. She took umbrage at that. "He'll have an accident," she said.

"He should be crawling over you," I thought, but didn't say.

Effectively, they had left their parenting to me, while they were enjoying the comforts of the front end of the plane. This started to really bug me. Not able to sleep, I got up and found the flight attendants in the galley.

I was curious. Did it often happen that parents flew in different cabins to their children? Was it allowed?

"There's a loophole," one of them told me. "If the parents book their kids in as 'unaccompanied children', then they can get away with it."

"Some parents are flying Business Class for work and want to take the kids, but can't afford the expensive seats," another attendant said. "It happens quite a lot."

They even do it when their kids are toddlers, apparently.

Well, I can see there might be legitimate reasons to travel in another class but later I spoke to a few parents who told me they usually work it so one adult is with one child up front, while the other sits at the back and they either swap during the flight or do one leg each in economy.

In my situation, the children were ostensibly old enough to look after themselves, but they were still kids. They needed a certain level of supervision. I didn't think I, or any other stranger, should be the one to do it.

"We keep our eyes on them," another attendant said. "If the other passengers are having a problem, we try to help out."

"How?" I ask. "There are a few seats available in Business Class, Miss Tulloch. Would you like to sit there and get some sleep?"

You bet I would. As I took my seat in the forward cabin, I waved to the mother. She was still oblivious to the problem she had created.

Traveller