Pete24601

I'm travelling from the UK to a conference in the US in a few months, via a short stop in New York to visit a friend. The LHR - JFK leg is in AA Premium Economy, and then a few days later the domestic leg from LGA in First on a Republic E175. The international ticket was actually booked through BA (the return is in Business on BA metal) while the domestic flight was booked with AA directly. I rarely fly for work and don't have any status.

Alongside my personal checked bag I'm going to have some special equipment with me for the conference (can't really say what), which is lightweight but somewhat bulky. I plan to buy a dedicated case for it soon but I'm not at all sure that it will fit within American's 62" size limit. Yesterday I actually knocked up a plywood box the size of the biggest acceptable SKB case to try to pack it all into, and if it doesn't fit then I'm going to need to buy something bigger and accept that I'm paying for oversize baggage. This kit has to come with me or there's no point in making the trip, and the tickets are already purchased so I'm stuck with American's policies.

My main question is, how do the mechanics of paying for and taking oversize baggage actually work? In Europe where there's more focus on weight, it's common to pay for excess baggage online in advance, at a discounted rate versus buying it at the airport. I haven't noticed anything like that on the American site, though I guess it may become available closer to the time when checkin opens. If not, how does payment work when checkin is mostly automated nowadays - do I need to find some special desk instead first? And, come to think of it, if checkin and bag drop is automated (in both directions on my last trip to Norway, I didn't interact with a human until passing Security) how are they checking the size? Is there some sort of laser scanning built into the dropoff now as well as the scale for weight?

Does anyone have any experience on how zealous AA tend to be on checking size? That is, if I have to be over, is it worth trying to be just a little bit over and hope they won't notice (but pay up with good grace, of course, if they do)? Or will they definitely notice, and if I can't get under the limit then I might as well make full use of the oversize allowance I'm paying for and get a nice big case with foam compartments to pack the kit neatly and logically, instead of trying to compact it? If AA will definitely charge me for going over 62", then I might as well go right up to BA's more generous limit of 35"x30"x17" (a total of 82", albeit with less flexibility on shape).

Any other thoughts or suggestions on travelling with big stuff welcome too - thanks.