Route image has the biggest factor on LF. Even a route with no competition will have a low LF until RI is built. If the route has competition, you may never be able to get over 40-50% LF depending on who else is serving it, and with what. Depending on the A/C and fuel you should still be able to make money, especially in the BWs. If you are still flying a 727 or 737-100/200 in 2010 on a long route at 50%LF, you wont make money, but if its a newer 737, or say A320 you should.