An engine (200; 300; 500) of an aircraft, comprising: a first fan (102; 302) configured to output a first air flow; a second fan (104; 304; 504) configured to receive a first portion of the first air flow and output a second air flow; a core configured to receive a first portion of the second air flow and generate a first stream, wherein the core includes a combustor (114; 314); and at least one valve (244; 344; 544) configured to assume one of at least three states in association with a generation of a second stream and a third stream based on at least one of the first air flow and the second air flow; characterised in that: the third stream is radially outboard of the second stream; and the third stream is formed based on a portion of the second stream, wherein when the at least one valve (244; 344; 544) is in a first of the at least three states the second stream and the third stream are generated based on a second portion (264; 364) of the second air flow, wherein when the at least one valve (244; 344; 544) is in a second of the at least three states the second stream is generated based on the second portion (264; 364) of the second air flow and the third stream is generated based on a second portion (262; 362) of the first air flow, wherein when the at least one valve (244; 344; 544) is in a third of the at least three states the second stream is generated based on a mixture of the second portion (262; 362) of the first air flow and the second portion (264; 364) of the second air flow, wherein when the at least one valve (244; 344; 544) is in the third of the at least three states the third stream is generated based on the second portion (262; 362) of the first air flow. a first fan (102; 302) configured to output a first air flow; a second fan (104; 304; 504) configured to receive a first portion of the first air flow and output a second air flow; a core configured to receive a first portion of the second air flow and generate a first stream, wherein the core includes a combustor (114; 314); and at least one valve (244; 344; 544) configured to assume one of at least three states in association with a generation of a second stream and a third stream based on at least one of the first air flow and the second air flow; characterised in that: the third stream is radially outboard of the second stream; and the third stream is formed based on a portion of the second stream, wherein when the at least one valve (244; 344; 544) is in a first of the at least three states the second stream and the third stream are generated based on a second portion (264; 364) of the second air flow, wherein when the at least one valve (244; 344; 544) is in a second of the at least three states the second stream is generated based on the second portion (264; 364) of the second air flow and the third stream is generated based on a second portion (262; 362) of the first air flow, wherein when the at least one valve (244; 344; 544) is in a third of the at least three states the second stream is generated based on a mixture of the second portion (262; 362) of the first air flow and the second portion (264; 364) of the second air flow, wherein when the at least one valve (244; 344; 544) is in the third of the at least three states the third stream is generated based on the second portion (262; 362) of the first air flow. the third stream is radially outboard of the second stream; and the third stream is formed based on a portion of the second stream, wherein when the at least one valve (244; 344; 544) is in a first of the at least three states the second stream and the third stream are generated based on a second portion (264; 364) of the second air flow, wherein when the at least one valve (244; 344; 544) is in a second of the at least three states the second stream is generated based on the second portion (264; 364) of the second air flow and the third stream is generated based on a second portion (262; 362) of the first air flow, wherein when the at least one valve (244; 344; 544) is in a third of the at least three states the second stream is generated based on a mixture of the second portion (262; 362) of the first air flow and the second portion (264; 364) of the second air flow, wherein when the at least one valve (244; 344; 544) is in the third of the at least three states the third stream is generated based on the second portion (262; 362) of the first air flow.