This excerpt taken from the HPQ DEF 14A filed Jan 29, 2008.
All Other Compensation Table
The following table provides additional information about the amounts that appear in the "All Other Compensation" column in the Fiscal 2007 Summary Compensation Table above:
For income tax purposes, the amounts included in NEO income are calculated based on the standard industry fare level ("SIFL") valuation method. For the CEO, the value of the first 25 hours of personal usage (which usage may include his spouse and other guests) is added to his income and grossed up. Other Executive Council members may use the corporate aircraft for personal purposes, subject to review by and approval of the CEO. The value of such trips is added to the executives' incomes and is not grossed up. The value of spousal travel on business trips is added to income, and this value is grossed up only if the spousal travel is requested by HP.