Sharemarket investors are over the moon about the prospects for Apple's next iPhone. But the company's top executive isn't sending the most bullish signal.

Apple CEO Tim Cook in recent days sold about $US43 million ($54 million) worth of company stock, according to a regulatory filing, reflecting a sale of all the net shares he was awarded last week for his job performance.

It's a nice time for Cook to get handed a big batch of Apple stock. Shares hit an all-time high on Tuesday and have climbed 41 per cent so far this year.

But it might not be the greatest time to sell Apple shares, if you believe the company is on the cusp of (further) greatness.