He sold 64,151 shares, but still holds 2,988 Apple shares worth approximately $1.8 million (as of Friday's closing price).

There has been some speculation that cashing in the shares suggests that Forstall is planning to leave the company, but points out that Forstall has two more retention bonuses in the wings - provided he stays with the company.

If Forstall sticks around and Apple achieves the predicted $1,000 per share within the next year, Forstall's share package could be worth a billion dollars, writes Fortune.

The shares Forstall just sold were part of a 120,000-share retention bonus that was granted in 2008.