The policy was different when you traveled. The sticker is your receipt, but you can't get a sticker anymore.

I know that... but, can you call someone from Scotland a Scottsman... (is the spelling correct?)...?

A male from Scotland is called a Scotsman...a female a Scotswoman collectively we are called Scots or Scottish.

As to your other questions. I would say we much prefer being called Scots rather than Brits. Same goes for the Welsh and the Northern Irish.

Of course some people think Britain only contains England and the English.
For the sake of world peace I shan't identify which country the worst culprits who think that come from.

Some of all this might change if Scots vote for independence, right?

Now, back to your regularly-scheduled reciprocity fee programming.

Is it reasonable to expect the airlines will understand this? Especially given that my sticker is in my former passport? I'm heading to EZE in May

It is absolutely reasonable to expect your airline will understand this. I had no issues on my recent EZE trip (LAN via LIM and GRU, docs checked @ SFO).

Ditto EastBay1K's experience for me, except in my case on AA out of JFK in January (so not even such a long time after the policy change).

The AA agents in the JFK Premium zone had never seen the "sticker in the passport" receipt before I showed them mine, but had no problem with it as it clearly shows validity for ten years.

Over Xmas 2013, my family will be connecting on UA from EWR to SCL via EZE. The connection out of EZE is on LAN (presumably UA has an interline agreement with LAN for baggage). Both the UA and AA websites now say they will not carry anyone to EZE without the bar code showing prepayment of the reciprocity fee. They refer questions to the Argentine authoritities. Of course, I e mailed them and got no response.

Does anyone have a link to an authoritative site which says if you are in transit at EZE you do not have to pay the fee? I will need something definite (not an opinion) in order to show United that they must let me board. For 6 people, I don't feel like paying $960 to see the inside of the EZE airport. Yet I don't want to take the chance that United says "sorry".

Of course, I will have LAN tickets showing onward travel 4 hours after landing at EZE, though it is not booked on the same record as my EWR to EZE flight.

Thanks for any assistance.

Sounds to me that you are travelling on separate tickets. What makes you so sure UA will check your bags straight through to SCL?

I will be traveling to BA with my Mother in June. I have been to Argentina twice in the past two years and have the sticker in my passoport. Will I need any other proof of payment other than the sticker in the passport?

Nope.

If it is not too late, you should probably try to avoid this and look into heading to SCL directly or connecting in a different city. EZE is a mess and you're likely going to run into heartache over this.

The airline should be able to tell you and make a note in your PNR that you are a transit passenger. I would call the consulate as well to ask them directly. Timatic indicates you might not ave to pay for up to 12 hrs transit but not entirely clear.