It's not against the rules, however, do consider that it's actually very easy if you want to compete on those routes, because 0.5 frequency routes tend to be a walkover.
Yes, but if it's one vs. one at that airport then the legit airline will only be able to compete on half the routes of the cheater airline. The 0.5 routes effectively doubles your airplane's hours by violating the laws of physics.
That's why I want the game to have a limit of one 0.5 frequency route per plane.
well really i think you should only be able to fly half routes to your own bases. like 1 frequency for any airport that is not a base/focus city. since our rule is that you cannot start a flight from anywhere except a base, it would only make sense that a one way flight could not come back from there the second day. so i see it as either that, or leave it as it is. it's a half frequency, with high fares, or one frequency with lower fares, but only making about 1.5 times the money. a little weird when you think about it..