The 27 states that will remain in the EU once the UK leaves the bloc have been asked by Brussels to explain “as a matter of urgency” how airlines they license will comply with its rules on ownership.

In a letter sent last week and seen by the Financial Times, transport commissioner Violeta Bulc said not every national government had detailed their plans on how carriers would meet “ownership and control requirements in all the possible scenarios” of Brexit.

These scenarios include a no-deal exit, where the UK leaves without an agreement.

Bulc asked transport ministers – “given the remaining short timeframe ahead” – to explain how affected airlines licensed by each country would meet the requirements on March 30, the day after Britain leaves the EU, and whether national authorities thought these measures sufficient.

The bloc’s rules stipulate that carriers must be owned and controlled by more than 50% of EU investors in order to retain their ability to fly freely in the bloc.

Bulc’s letter represents a ramping up of no-deal preparations with just over two months before the UK’s departure, according to the FT.

She had previously written to countries in July 2017 to clarify how they intended to meet the regulations.

Some companies – including British Airways and Iberia owner International Airlines Group – have yet to ensure they will reach that threshold after Brexit, when investors who are UK nationals will no longer count towards the tally.

Both Ryanair and easyJet have said that they will remove voting rights from non-EU shareholders to meet the threshold if need be, while both have applied for secondary operating licences to allow flights to continue — Ryanair from the UK, easyJet from Austria.

IAG, which is a Spanish company that has its headquarters in the UK, said: “We are confident that we will comply with the EU and the UK ownership and control rules post-Brexit.”