Looking from the airplane, I thought these islands were truly beautiful.

Literal

Airplane [from-から] look [if-と], these islands [subject-が] truly beautiful [quotative-と] thought.

Frames the beauty as the speaker's past thought rather than as objective fact: ~と思った quotes the inner reflection. ほんとうに ('truly, really') intensifies the adjective. 飛行機から見ると uses the conditional と to set up the aerial vantage point.