A senior Airbus executive has warned the company's future investment could be hit if Brexit disrupts the movement of talent and products.
"At the moment we're continuing to invest because we take the view that Airbus in the UK is an integral part of the family of Airbus, so we're still highly committed to the UK," said Tom Williams, chief operating officer and president of commercial aircraft at Airbus.
Giving evidence to the Treasury Select Committee on the UK's future economic relationship with the European Union, he said: "It's only the success of Airbus as a highly integrated company that gives us the success that we have and the impact that we have on employment and the jobs we create, the money we spend in the UK."
"We've got a lot of Brits working in Europe and a lot of French and Germans working here in the UK, so for us as an international company, that's what we need to have - a fairly seamless process - and anything that disrupts that model will create inefficiency and could affect our long-term competitiveness."
He also suggested Washington would be "more than delighted" should that happen, and the US would make decisions based on what would benefit Airbus' US rival Boeing.
Airbus has 600 EU workers in the UK and 1,800 Brits in Europe, which Williams said was crucial for "career development". Williams also pointed to the company's current setup where wings are built in one factory in the UK and then transported immediately to other plants in Europe.
"If that starts to change it won't change our decision day by day, but it could in the longer-term, so as we come towards the end of this decade, when there are perhaps bigger decisions about longer-term product policy and next investments then it could become a deciding factor," Williams said.
The chief executive of the Society of Motor Manufacturers and Traders (SMMT) also said companies were "at least sitting on their hands until there's a bit more clarity" regarding investment decisions.
Mike Hawes said while Nissan's committment to building its next Qashqai SUV in Sunderland was positive, conclusions couldn't be drawn from just one manufacturer. A different company "will potentially be in a very different position", he added.
"I sense certainly that the amount invested over the last 12 months will not be as high as the preceding one, two, three years."