Delta to JFK is already planned to be year round and bookable as such,
Skip, I'm afraid you are digging a bigger hole for yourself. See the words I've put in bold print from LAX's original post.
Continuing to take cheap, sarcastic digs at a fellow poster who you know won't respond, (even if your intention is to try and provoke him to do so), isn't contributing in any meaningful way to the thread in my opinion. You're better than that and provide good debating points at times even if some of us don't always agree with you.
Returning to the question of flights to New York from MAN, apart from excess demand during busy periods which may be diverted to fill seats from LHR, it would be interesting to know also how many savvy cost conscious travellers may be choosing to fly via DUB or KEF at the expense of MAN's direct services. A friend is planning to go to Seattle later this year by Icelandair simply because of the fares.