Thermal management system

A method of operating a thermal management system for a gas turbine engine, the method comprising:

• determining the gas turbine engine is in a first operating mode;
• transferring heat from a first heat source exchanger to a heat sink system while bypassing a second heat source exchanger via a second bypass line around the second heat source exchanger in response to determining the gas turbine engine is in the first operation mode, the first heat source exchanger thermally coupled to a first system or component of the gas turbine engine;
• determining the gas turbine engine is in a second operating mode, the second operating mode being different than the first operating mode;
• and
• transferring heat from the second heat source exchanger to the heat sink system while bypassing the first heat source exchanger via a first bypass line around the first heat source exchanger in response to determining the gas turbine engine is in the second operation mode, the second heat source exchanger thermally coupled to a second system or component of the gas turbine engine,
• wherein the second system or component is different than the first system or component.