From the Airbus website:
http://www.airbus.com/be-an-airbus-supplier.html:
Around 80% of Airbus’ activity is sourced. The company works with more than 12,000 suppliers worldwide that provide products and services for flying and non-flying parts. Airbus continuously develops its supplier base, with an overall sourcing volume across the company valued at approximately €49.6 billion. Airbus has identified global sourcing as one of its long-term objectives and aims to source 40% outside Western Europe and the U.S. by 2020. Airbus’ external procurement is equivalent to over two-thirds of the company’s revenues
Why, therefore, should it matter if the UK is outside the EU?