What Are The Responsibilities Of A Part 121 Dispatcher 

The responsibility of a Part 121 dispatcher is clearly stated in § 121.533.

In § 121.533(b) it states:

The pilot in command and the aircraft dispatcher are jointly responsible for the preflight planning, delay, and dispatch release of a flight in compliance with this chapter and operations specifications.

The PIC and aircraft dispatcher are jointly responsible for:

1. Preflight planning
   • calculating weight
   • looking at weather (METARs, TAFs, Prog Charts, etc.), NOTAMs, MELs, etc
   • planning alternates
   • planning routes
2. Delay
   • Delay due to weather or any other situation for the safety of the flight
3. Dispatch Release
   • The legal binding signage by the PIC and dispatcher that the flight passes within all regulations and is safe to fly
   • Contains all the information about the flight (Airports, VFR or IFR, Fuel, Aircraft ID, Trip ID, Weather / NOTAMs)

Additional responsibilities in § 121.533(c) states: 

The aircraft dispatcher is responsible for—