California Code, Revenue and Taxation Code - RTC § 25101.3

(a) The time in state is the proportionate amount of time, both in the air and on the ground, that certificated aircraft have spent within the state during the taxable year as compared to the total time everywhere during the taxable year. This factor shall be multiplied by 75 percent.

(b) Arrivals and departures is the number of arrivals in and departures from airports within the state of certificated aircraft during the taxable year as compared to the total number of arrivals in and departures from airports both within this state and elsewhere during the taxable year. This factor shall be multiplied by 25 percent.

(c) The time in state factor shall be added to the arrivals and departures factor.

(d) The figure produced by application of subdivision (c) equals the allocation to be applied to the original cost of property owned or rented by the taxpayer determined under the provisions of Section 25130.

(e) If annual statistics for the taxpayer's taxable year are not available, statistics for representative periods designated by the Franchise Tax Board shall be used provided that permission to do so has been granted to the taxpayer by the Franchise Tax Board.