I'm also wondering whether the EU has taken a position on the status of UK rights under current ASAs for UK airlines to operate flights to/from non-EU countries. Traditionally, these were bilateral (most notoriously Bermuda and Bermuda II) but I think more recently have been agreed at EU level for the entire EU because ASAs were an EU competence rather than a Member State competence.

I wonder whether there might in theory be a possibility that on Brexit day, UK airlines would lose all rights to operate between points in the (remaining) EU, and between UK points and (remaining) EU points because no ASA is in place to replace the invalidated current EU arrangements; and also between the UK and non-EU points because there are no longer any effective ASAs between the UK and non-EU countries that allow for such flights. BA might be limited to doing domestic flights only!