Here's a little secret that readers who are childless - or 'childfree', depending on your perspective - may be unaware of: Airlines let parents of young kids pack heaps of extra stuff in their luggage. For free.

But, in these pay-for-what-you-get days of harsh economic reality, for how long can this nifty bit of parental aid continue?

Most businesses are pretty cool about kids. A smart cafe owner will have a playpen - or 'holding cell', depending on your perspective - in the hope of attracting parents to spend money on flat whites and muffins midweek.

But when it comes to airlines, you kid-free fliers are effectively subsidising the luggage of us parents. (For which I'd like to say: Thanks.)

When my family of four (with two kids under the age of four) flies, we turn up at the airport with the adults' luggage (generally) conforming to the approved minimalist rules.

But when it comes to the kids' stuff, the airline lets us stick piles of stuff through for free. They have rules, but no staff member has ever raised so much as an eyebrow at the truckload of gear we shove into the hold. The more frazzled we look, the more obliging they are - bless 'em. Often they'll pull out massive zip-lock bags and encourage us to pour stuff in.

And what a pile of stuff there is. Anyone who's gone as far as a short drive across town with sprogs will know that the car is quickly filled with baby-related kit - nappies, pram, spare nappies, a change of clothes, more bloody nappies, a back-up change of clothes and a back-up spare change of clothes and, of course, the engineering wonder that is the portacot - the Rubik's cube of fatherhood.

All of this and more must be packed away for a flight. And for God's sake don't forget to bring the favourite soft toy.

But, as the recent discussion about charging passengers for airline tickets relative to their weight illustrates, the days of easy flying could be coming to an end. Times are tough and airlines are always looking for ways to 'rationalise'.

That bulky portacot is taking up space in the plane's hold that could be used by a fare-paying traveller or lucrative items of cargo.

I hope airlines continue to make life easy for travellers with kids, even as we get to the stage of life where the portacot is no longer needed. Parents need every bit of help they can get.