1: Dealing with passengers in LA.
- The airline would most likely board these passengers on other flights going to the same destination but at a later time if they have seats left over on those flights. If that doesnt clear up the mess they would lease and aircraft from another airline or convert the tickets to other airlines flying to the same destination IF these other airlines are part of the same group like for example Star Alliance (SAS, Lufthansa etc).
2: The PAX in Iceland would have to sit an freeze on that island for a while until the airline could lease another aircraft to go to Iceland to pick them up. OR they might be booked on flights going from Iceland to LA with other airlines.
3: the U/S aircraft on iceland could if the state of registry gives it's approval be flown to the nearest airport where it can be repaired. If this is not possible, a team of mechanics would have to fly to Iceland with spare parts to repair the aircraft on location.
Hope this is some help...
Kind Regards
Tim