There are a few airlines that allow it for personal travel. FX allows jumpseats outside the cockpit only. UPS, CO, WN, Frontier are the only ones I know that allow cockpit jumps for MX for regular travel. Of course in an AOG company business situation all bets are off and mechanics get the blessing to ride up front at virtually all airlines. When I worked at NW it was pretty tough for MX to get it if the a/c was full and the jumpseat was open. There were a few pilots who made exceptions and let them ride but only with the blessing of maint control but for the most part at NW captains refused the jumpseat to MX unless it was company business/must ride situation. My personal take is that especially for line maintenance FAM rides should be required just like it is for dispatchers several times a year.