Aircraft powerplant with boosted turbine engine and fuel cell system

A powerplant for an aircraft, comprising:

• a first turbine engine including a first engine flowpath, a first engine compressor section, a first engine combustor section and a first engine turbine section, the first engine flowpath extending through the first engine compressor section, the first engine combustor section and the first engine turbine section from a first engine flowpath inlet into the first engine flowpath to a first engine flowpath exhaust from the first engine flowpath;
• a second turbine engine including a second engine flowpath, a second engine compressor section, a second engine combustor section and a second engine turbine section, the second engine flowpath extending through the second engine compressor section, the second engine combustor section and the second engine turbine section from a second engine flowpath inlet into the second engine flowpath to a second engine flowpath outlet from the second engine flowpath, and the second engine flowpath inlet and the second engine flowpath outlet each fluidly coupled with the first engine flowpath;
• and
• a fuel cell system including a fuel cell, a fuel circuit and an air circuit, the fuel circuit extending through the fuel cell and fluidly coupled with and upstream of a first fuel injector in the second engine combustor section, and the air circuit extending through the fuel cell and fluidly coupled with and downstream of a bleed from the second engine flowpath.