we've just received our ticket info from charter travel and the letter says that we should arrive at the airport 4 hours before the flight leaves, is this not excessive?

we've already got our seats booked, why do we need to arrive so early? we're staying at the Arora near gatwick on teh friday night and as our flight is at 10.55 I reckoned that 9am was sufficient time to book in our luggage etc, can you advise?

Elaine