1. European Commission, Flightpath 2050.
https://ec.europa.eu/transport/sites/transport/files/modes/air/doc/flightpath2050.pdf
. Assessed 01 July 2017
2. Airbus S.A.S., O & D.
http://www.airbus.com/company/market/orders-deliveries/
. Assessed 1 June 2017
3. Boeing, Orders and Deliveries.
http://www.boeing.com/commercial/#/orders-deliveries
. Accessed 5 July 2017
4. MTU Aero Engines, Pilot concepts for commercial applications: geared turbofan™ and other concepts.
http://www.mtu.de/technologies/technologies-for-the-future/engines-to-come/commercial-engines/
. Accessed 5 July 2017
5. ISO 16290:2013 Space systems—Definition of the Technology Readiness Levels (TRLs) and their criteria of assessment. ISO. 14 October 2013.