Originally Posted by NickB

They certainly could not pick up pax in JFK for another US destination as cabotage, even consecutive cabotage, is streng verboten under the US-EU agreement (or indeed any other ASA with the US as they will not allow cabotage by foreign carriers). OTOH, I believe that a JFK-Canada flight would be OK under the US-EU agreement. I have not looked at what the story is regarding the Canada side of the story, though, since it would also have to be authorised under the relevant UK-Canada (or EU-Canada?, not sure if there is one of if it is still national bilaterals) agreement.