A jet engine comprising: an inlet configured to take in air; a combustor configured to combust fuel by using the air; and a fuel control section configured to control supply of the fuel, wherein the combustor comprises: a fuel supplying section configured to supply the fuel; an injector (20;20a) having an opening (30-1,30-2,30-3,30-4,30-5) configured to inject the fuel supplied from the fuel supplying section; a pipe (43, 44-1, 44-2, 44-3, 44-4, 44-5; 43a-1, 43a-2, 44a-1, 44a-2,44a-3,44a-4,44a-5) configured to send the fuel from the fuel supplying section to the opening (30-1,30-2,30-3,30-4,30-5); and a flow-path cross-section area adjusting section (42-1,42-2, 42-3, 42-4, 42-5; 42a-1, 42a-2) provided for the pipe (43,44-1, 44-2, 44-3, 44-4, 44-5; 43a-1, 43a-2, 44a-1, 44a-2, 44a-3, 44a-4, 44a-5), wherein the fuel control section is configured to control the fuel supplying section in response to a command of an autopilot to supply a total flow rate of fuel to the injector (20;20a), characterized in that the fuel control section is configured to control the flow-path cross-section area adjusting section (42-1,42-2,42-3, 42-4, 42-5; 42a-1, 42a-2) based on an airspeed of the jet engine and/or an altitude of the jet engine to change the cross section area of the pipe (43,44-1,44-2,44-3,44-4,44-5; 43a-1, 43a-2, 44a-1, 44a-2, 44a-3, 44a-4, 44a-5) such that a penetration height of the fuel is controlled and such that the fuel passes through a flame stabilization possible region. an inlet configured to take in air; a combustor configured to combust fuel by using the air; and a fuel control section configured to control supply of the fuel, wherein the combustor comprises: a fuel supplying section configured to supply the fuel; an injector (20;20a) having an opening (30-1,30-2,30-3,30-4,30-5) configured to inject the fuel supplied from the fuel supplying section; a pipe (43, 44-1, 44-2, 44-3, 44-4, 44-5; 43a-1, 43a-2, 44a-1, 44a-2,44a-3,44a-4,44a-5) configured to send the fuel from the fuel supplying section to the opening (30-1,30-2,30-3,30-4,30-5); and a flow-path cross-section area adjusting section (42-1,42-2, 42-3, 42-4, 42-5; 42a-1, 42a-2) provided for the pipe (43,44-1, 44-2, 44-3, 44-4, 44-5; 43a-1, 43a-2, 44a-1, 44a-2, 44a-3, 44a-4, 44a-5), wherein the fuel control section is configured to control the fuel supplying section in response to a command of an autopilot to supply a total flow rate of fuel to the injector (20;20a), characterized in that the fuel control section is configured to control the flow-path cross-section area adjusting section (42-1,42-2,42-3, 42-4, 42-5; 42a-1, 42a-2) based on an airspeed of the jet engine and/or an altitude of the jet engine to change the cross section area of the pipe (43,44-1,44-2,44-3,44-4,44-5; 43a-1, 43a-2, 44a-1, 44a-2, 44a-3, 44a-4, 44a-5) such that a penetration height of the fuel is controlled and such that the fuel passes through a flame stabilization possible region. a fuel supplying section configured to supply the fuel; an injector (20;20a) having an opening (30-1,30-2,30-3,30-4,30-5) configured to inject the fuel supplied from the fuel supplying section; a pipe (43, 44-1, 44-2, 44-3, 44-4, 44-5; 43a-1, 43a-2, 44a-1, 44a-2,44a-3,44a-4,44a-5) configured to send the fuel from the fuel supplying section to the opening (30-1,30-2,30-3,30-4,30-5); and a flow-path cross-section area adjusting section (42-1,42-2, 42-3, 42-4, 42-5; 42a-1, 42a-2) provided for the pipe (43,44-1, 44-2, 44-3, 44-4, 44-5; 43a-1, 43a-2, 44a-1, 44a-2, 44a-3, 44a-4, 44a-5), wherein the fuel control section is configured to control the fuel supplying section in response to a command of an autopilot to supply a total flow rate of fuel to the injector (20;20a), characterized in that the fuel control section is configured to control the flow-path cross-section area adjusting section (42-1,42-2,42-3, 42-4, 42-5; 42a-1, 42a-2) based on an airspeed of the jet engine and/or an altitude of the jet engine to change the cross section area of the pipe (43,44-1,44-2,44-3,44-4,44-5; 43a-1, 43a-2, 44a-1, 44a-2, 44a-3, 44a-4, 44a-5) such that a penetration height of the fuel is controlled and such that the fuel passes through a flame stabilization possible region.