There may be no more beautiful approach on a destination than the flight to the near-atoll of Aitutaki in the Cook Islands. If you are flying in from Rarotonga (the most common option for foreigners), you will be delighted with views of the entire lagoon before landing.
Make sure you pick a window seat for this one. Flying over Aitutaki provides views normally reserved for helicopters and is even more gorgeous than taking a boat through the Lagoon. Of course the views after you land are pretty awesome as well.