Where do you land if there is an emergency during a trans-atlantic flight?

They could. Lindbergh flew across the Atlantic without autopilot.

Technically is you are flying domestic you are not flying over foreign airspace. If flying IFR you must file one. Needless to say when filing a flight plan you must decalre if you are domestic of international flight.

Pilot can do anything he judges best for his flight.

That would be the ground prox system on the aircraft it lets the flight crew know how far they are above the ground during an approach to the landing runway.

The DC10 was an excellent aircraft, with a long and successful service history. They are still flying in many countries, and in the US you see lots of them with the freight haulers.
There were, unfortunately, a few (very few) high profile crashes - which is probably what you refer to. The infamous "engine drop" issue was bad maintenance - not a problem with the aircraft design. And the Sioux City crash (pilot Al Haynes) was caused by a truly unlikely event that simply proves that even low odds can happen. [An uncontained blade failure on the #2 engine ejected "just right" (or just wrong) and cut the one small spot where all the control surface hydraulic lines came briefly together.]
The reason that DC10's are no longer in primary service is attributable to two things:
1. Older fuel hungry engines (3 of them), compared to the more fuel efficient twin engine design. And the changes to ETOPS regulations that now allow twin engine airliners to fly trans-ocean.
2. Certification of the aircraft with a three-person crew, in stead of the cheaper two-person flight crew common now. [The freight haulers get around this by cross training the loadmaster (only needed on the ground) to also be the flight engineer (only needed in the air).

Aircraft too heavy. Weight is extremely valuable/expensive and the weight of a parachute system would be too heavy and costly, sacrificing room for paying passengers.

Michele,
Airbus 321 can't fly between LHR to JFK. Aircraft range is 5950km and the air distance between LHR and JFK is 8,112 km..
with regards.
jaijith

Students and certificated pilots both are required to remain current and to have a check ride (flight review with an instructor) every 24 calendar months. The ones you're seeing are probably going out to the practice area to practice their flight maneuvers. If a pilot doesn't practice regularly his or her skills can deteriorate rapidly.