"That airplane is the fastest of all airplanes."
Translation:Dat vliegtuig is het snelst van alle vliegtuigen.
To me, it seems that you should leave 'van alle/der vliegtuigen' out if you use 'de snelste', but I'm not entirely certain. Besides, it's not a big issue in my opinion; people will understand it regardless of which one you choose. By the way, 'der', 'des' etc are very oldfashioned words which are not used in modern Dutch any more, people might find it a bit strange if you use these forms in your speech. But if you try your best, I'm sure people will help you ;)