The OP raised the scenario of an airliner ditching at 30W.
This scenario constitutes a
Mass Rescue Operation.
I recall attending a large, high level, well attended, international SAR conference some years ago (probably over 10) that discussed responses to MRO. The conference concluded that no country was well placed to deal with an MRO, particularly that of an airliner ditching at range (as opposed to a sinking ship).
Delegates were brigaded into syndicates and played out scenarios to explore the issues. There was a reasonable cadre of UK RAF Nimrod and SARF attendees (of which I was one). After spending two days with our international colleagues exploring how such a scenario would be managed, it became very clear to all that, other than in a limited number of very narrow circumstances, a good outcome for an airliner ditching at range (even with rapid MPA response and rapid location) was unlikely.
At the risk of over simplifying the challenges (we did a fair bit of maths and plotting over the week) the main problems are not associated with location but with the inability to either drop enough ASRA (or ASRAesque) equipment or to actually recover enough people. Once you're in the water your stuffed (if you're really lucky and get into one of the airliner's liferafts you may do better).
Assuming a passenger capacity for a 777 of 300 or so people (it's more likely to be higher) and then divide that by the number of liferafts you need to drop. Multiply that by the number of aircraft needed to carry them.
The only good outcome is if there is surface traffic nearby with the capacity to assist. For MRO at range, other than post-hoc location, air capability is pretty helpless really.
Sun