Part of the problem is the amount of passengers. Players with a hub on ATL will get more passengers than players without a hub. Big players with good powerful hubs, like travelhouse, steal your passengers to the point where no passengers remain (0.0% LF).
As soon as another player opens a hub, the first large player gets upset because her LF drops. At that moment she spots a beech, and the player owning that beech has done it.
Also, don't be afraid to change your plane. Just make sure you set a new price when you alter the amount of trips and/or the airframe. Yes, you will trigger another bug when you do that (everybody needs to recalculate their prices then) but you don't want to see 100% LF.
Dropping your price will not always work. One round trip a day, price 1 dollar, and still a load factor of 0.00% was often reported last round. I see no reason why this round would be different. The market for such a route is saturated, and you cannot get a fair share anymore. It is not last-in-first-out so it can happen to you even if you setup the route initially.