Refer to the input text as context and select the correct relationship between 'Airbus' and 'aircraft' from the available options.
Options: product/material produced, stock exchange, platform, manufacturer

The slump in sales of very large aircraft has raised questions about how long Boeing and European rival Airbus Group NV can keep building double-decker planes, with 2015 a make-or-break year for both.
product/material produced