LONDON — Britain voted almost exactly two years ago to leave the European Union, and months before it must agree on a withdrawal deal or crash out of the bloc, much remains undecided. Too much, for at least one company.

On Friday, the European aerospace giant Airbus, which makes commercial airliners like the A380 as well as military aircraft, delivered a stark warning to the British government: Give us more clarity, or we might leave the country.

The announcement, outlined in a published report and in remarks by a company executive, was unusually direct, offering a window into businesses’ concerns as Britain runs out of time to make a deal with the European Union. Though few companies have spoken out publicly, trade groups have warned repeatedly that notice of any agreement was needed to help plan for future investments and adjust accordingly.

But with Britain set to leave the bloc at the end of March, few details have been ironed out. Banks based in Britain do not know what access they will have to Continental markets, pharmaceutical companies do not know how their drugs will be regulated, and airlines are unsure whether they will need to create separate entities with headquarters abroad.