Heya there.
American Airlines and Delta both offer direct flights from JFK to Pittsburgh. Tickets are usually around $130 or so if you reserve early enough.
Whatever you do, don't take the bus from NYC to Pitts. I did that once and it was a big mistake. Couldn't get up and stretch, stuck in an uncomfortable seat for 8 hours. You can take Amtrak and it's more comfortable than taking the bus, but it's more expensive for some reason. Flying is probably the best bet.
Good luck!