Although Federal Govt asserts ownership rights on employee miles earned on federal travel, airlines do not recognize that assertion. However, employees are employees and subject to employer rules. Federal Govt employees may use FF miles earned on Govt paid travel (ref: FTR and JTR sites' FAQs) for free tickets for subsequent official govt trips or upgrades to biz class (only--never first) when specifically authorized and then only when the flight time exceeds fourteen (yes, 14) hours. And in the latter case of a flight time greater than 14 hours, ONLY when the employee must start work IMMEDIATELY upon arrival (no rest period of any amount) at the business location. Employees who do other than the above are risking their pensions. Removal from the Federal Service is an employer option. Enforcement and interpretation nuances vary with organizations but the Federal Travel Regulations apply to all Federal Employees.