Ask for details. Don't be put off by the intial warm and fuzzy reply.

Your aircraft could have been stuck elsewhere because of weather conditions on it preceding rotation. In this case, standby equipment could have been used: if it wasn't, you or your representative will want to know why.

If you want to take it further, don't mess around with endless correspondence with the airline: they will wear you down. Contact the national enforcement body (http://ec.europa.eu/transport/themes...ent_bodies.pdf), use the courts, or employ one of the commercial concerns that take on your case for a percentage of the compensation received.