Can you help with this regulation? I'm a member of IATA and have never seen this; however I haven't been a long time member. IATA is more of a representation organization setting standards and procedures. So that ticketing and cargo and other areas speak the same language plus they help deal with governments and such. From what I've seen IATA can't regulate anything. IATA surely can not form a policy that goes against ICAO or DOT or ECAC, and they can't form a policy that is universal applied to everywhere. They can set standards / policy / guidelines for airlines and travel and passenger safety and such, but it is still up to the regulator agencies to regulate, then it is up to the airlines to decide their own policies operating under their respective legal regulators.

I did do a quick search and it could be that this info isn't in my area of what I can see, but I didn't see anything under IATA about this (of course not all policies are on the web and you don't get all policies for every aspect when you are a member). So I can send an email about this to IATA if we want to get to the bottom of it but I've got nothing from looking through my info.

Reason I'm bringing this up, when I flew with my kids on a US Domestic Carrier even though I purchased them their own seats, I was in the same position and asked about it, and I was told on the airline I was using that you'd need a seat on the return. As it is international you have to show the passports and if it goes against company policy then you're busted.

I can picture Ticket Agents letting you slide on this if the flight isn't full especially overseas, but if the OP gets a phone conversation that says the child has to be two before departure and if they turn over that age during the trip they can return as a lap child then I'd get it in writting and that still might not solve the problems you might encounter. If you get an check in agent and they say NOPE, our rules are the opposite of what you are told then you're stuck with purchasing a one way ticket on the return. If you have their rules in writting I'd ask for specific airline guideline page number and title and paragraph where it is listed out in their rules and reg's so you can quote it and / or take a copy also so you can show them. And if they go still go against you after someone else telling you it's OK then you still have to get a one way ticket but you can fight it when you get home.

Again however I have to point out that it is much safer to get a child's seat and usually more enjoyable. Some airlines offer really nice children's seat deals that aren't that expensive. So you need to do a cost savings analysis, is it worth it to search this and fight this and risk being told you need to purchase a one way ticket on return, or is it better to just get the discounted child's seat? That's you're personal decision.

Now, rules on many issues vary depending if you are using a US Domestic or Foreign Airline. And rules are different for international and domestic travel of course, so if you are using one airline then it will be easy (easier, hopefully) to get to the bottom of this, if you are taking multiple airlines, then I would suggest getting the same info from all three which will make it much more difficult; but definitely get a reference to the rule book, page XX of XXX book under paragraph XX subclass XX etc....

As far as getting information from a travel agent goes in regards to rules and regulations, don't trust it. Just because you have an IATA agency doesn't mean you are an expert in anything especially quirky rules like this. There's no magic test you take to be licensed by the IATA that says you're an expert in anything and it is a relative simple process to get an IATA license (costly but simple). It's my experience FTers know more then TA's know, so go straight to the airlines.

That's my two cents......... That and a dollar might get you a coffee