I've been planning a trip to Europe and flights to Heathrow and Barcelona from Tucson are < $1000 until Mid may. However, they all go through Atlanta or Houston

I've been planning a trip to Europe and flights to Heathrow and Barcelona from Tucson are < $1000 until Mid may. However, they all go through Atlanta or Houston instead of NY. Maybe it's a NY->UK premium? Strangely, the same flights direct from Houston or ATL to London are more than the ones from Tucson with layovers.