Lisalippy:
39. The answer is a phrase which means "just the thing". It also featured in very early radios - try following up on crystal sets.
86. This is the nickname of a very famous broadcasting organisation. You will then see how the clue fits in neatly.
89. Captain Cooker is the animal. Then a word for a very long time. Then a word for appointment (as in job). The whole thing is a sort of airmail (not exactly what you would think of first!)
Paul