According to EU legislation, to benefit from the “open skies” policy (in other words, to operate freely on intra-EU air routes) airlines must have 50% + 1 of their shares held by EU shareholders.
Today IAG does not meet this requirements if its British investors are regarded as non-EU, something that could happen with a no deal Brexit (and, therefore, without alternative agreements for aviation regulation). In fact, currently 47.5% of its capital is held by non-EU investors, even if British investors are considered as EU.
Therefore IAG has decided that any non-EU investor which buys shares from today onwards will have their voting rights suspended and will have to sell them within 10 days. If they do not, IAG itself will buy these shares for repayment at the lowest price between: 1) book value. 2) Average share price in the London stock market the day on which the investor bought them. For the moment British shareholders will not be treated as non EU shareholders. Its current free float is 54.7%, but its principal shareholders are non EU and that is an operational risk for IAG depending on the post-Brexit aviation agreements: 21.52% Qatar airways; 13.25% Capital Group; 4.56% Black Rock; 3.97% Standard Life Aberdeen; 2.13% Invesco.
However, the Parliament approved then a package of measures to ensure the connection between Spain and the EU in the event of a no-deal Brexit. It consists of a package of measures which now need to be approved by the State Council and then ratified by the Commission and European Parliament. This package of measures would allow airlines to continue their activities until March 2020.
The short term impact on the share value will be negative because it limits the entry of shareholders, although this measure is necessary to protect its activities (aviation routes) facing the uncertainties Brexit represents, whatever its final outcome. This measure will not resolve the problem definitively because it cannot be ruled out that, under a no deal Brexit, the current British shareholders will be regarded as non EU.