https://www.ft.com/content/b638551a-68c3-11e7-8526-7b38dcaef614
https://publications.parliament.uk/pa/cm201719/cmselect/cmniaf/329/329.pdf
https://cer.org.uk/sites/default/files/bulletin_114_js_st_article1.pdf
http://openeurope.org.uk/today/blog/will-brexit-ground-flights-europe/