How Is USA Mail Transported Overseas?

I recently won an international auction (UK) and got to wondering.....

Is overseas mail routinely transported by air, or ship. I assume "air", but obviously am not certain.

Thank you,
Mobilman44

Air. Unless the seller is sending via International Economy, which is cheaper, but much slower.

I would also say by air. I've read that it is usually more economical to mail by air unless it is a very large or heavy item.

Air. There are usually weight limits for it. For Great Britain, it is 2 kg = 4.4 lbs. Royal Post says to expect it in 5-7 days but perhaps more depending on where you are in the US.

2 kgs is a key break point, both domestically and internationally. A 2 kg small parcel to the US costs £18.30, with £1.70 per 250 gm increments up to 5 kg. A reasonably substantial stamp album would be likely to be outside the "small parcel" criteria. 2 kgs by sea would be £12.05. Much depends on the method that the auction house uses. Being risk-averse, they tend to use the straightforward but expensive.

https://www.royalmail.com/sites/def...rch-2018.pdf

Thanks all for the info, and Thank You GeoffHa for the link - that's pretty interesting to me!

Gonna take a wild guess here that the reason International Economy is much slower is not that it travels surface, but that it travels via surplus air transport space purchased on the secondary market.

Cheaper. Slower. Done.

Cheers,

/s/ ikeyPikey