Minor clarification. In California it is the Interstate Commerce Exemption (aka ICE) which requires that 1) possession is taken outside of CA and 2) the majority of the hours in the six months after the plane first enters CA are interstate and for a business purpose. Colin's example of commuting to Vegas is a perfect case as every flight to Vegas would be interstate and for a business purpose.
Note that the owner controls both the numerator and denominator that determines the "majority". In an extreme case, if there was only flight, and it was interstate, the criteria would be satisfied.
There are services, some are attorneys, others not, that will instruct and facilitate the documentation, file the exemption with the state, etc.
It does require meticulous documentation, but the business purpose need not be a simple or clear cut as Colin's example. This is strictly about CA Use Tax.
The "Hobby Rule" is for the IRS and refers to the requirement that a majority of the hours flown be for a business purpose in order to deduct expenses, including depreciation, on Federal income taxes. The percentage of business use must be more than 50% and then that percentage of expenses may be considered a business expense.