This was 10 yrs ago:

Daughter's band was invited to a festival in Bahamas so there were 200 including parents and 400+ pieces of luggage plus instruments.

Dealt with AMEX corp travel department and it was cheaper to charter. Plus:

• You can carry what ever your group needs (Think Sousaphones). We took our luggage/instruments to planeside and put on on the conveyor ourselves.
• Bring your own water/soda/juice fastfood.
• You save by not paying for terminal baggage handling and flight catering.
• Direct flight to and back from destination. We flew out of a local smaller airport which which made gathering the group together much easier.
• Fly almost at the exact time you want (ATC permitting)