No as it is part of the UK. You don't need one from Southern either. You will generally need photo id though so you can prove who you are (like a photocard driving licence). Your probably best ringing the airline you fly with to check before you get to the airport.
I travel by air every other day, and sinse 9/11 every airline now requires a passport or photo ID before you can check in, this includes domestic travel i.e england to england or in your case nothern ireland to england..it not worth the hassle of not having one