Ultra unbundled Spirit Airlines, perhaps the most extreme example of low-fare U.S. carriers, just launched eight new routes aimed at filling in gaps in its route system. The upshot is more cheap seat options for consumers willing to pay extra for virtually every amenity on the aircraft. On May 25,  Spirit launched nonstop service from Baltimore/Washington (BWI) to Oakland on a seasonal basis. A couple of other year-round trans-cons also were begun: BWI – San Diego and BWI – Seattle/Tacoma. The new Baltimore/Washington routes increase Spirit’s ability to compete a bit more with BWI powerhouse Southwest Airlines, which unbundles its product far less aggressively than Spirit.  Southwest’s popular ‘Bags Fly Free’ policy is illustrative of the strategy. At the same time the BWI routes took off, Spirit began flying nonstop from Detroit to Oakland and Seattle/Tacoma on a seasonal basis. Finally, Spirit just launched a trio of new nonstops from New Orleans (MSY) to Baltimore/Washington, Cleveland and Orlando. The start of the new runs comes as  Spirit has taken delivery of its 100^th Airbus narrowbody. The carrier flies A320 family jets, and it paints them vivid yellow. There are a couple of advantages to this: first (and arguably most important) they’re easy for other airplanes to spot aloft in crowded airspace. Second, they stand out unmistakably on congested airport ramps. Spirit can use them as flying billboards. The last time a U.S. airline slathered its entire fleet with this much yellow was during the days of Northeast Airlines’ ‘Yellow Birds.’ Even then the upper portions of the aircraft were white. Northeast merged with Delta in 1972.