The European Commission has launched a formal investigation into Etihad Airways’ shareholding and control of several European airlines, including Air Berlin and Air Serbia, Aviation Week has learned.

The EC has also launched a parallel probe of Delta Air Lines’ 49% stake and control of Virgin Atlantic.

Commissioners have doubts whether the Etihad and Delta investments are in line with European Union rules on ownership and effective control of EU airlines. The tests of ownership and control are separate and both have to be met to achieve compliance and for an airline to keep its EU “nationality” and traffic rights.

The Commission has sent letters to the German government and to the government of Serbia requesting detailed information on Etihad’s influence and control of Air Berlin and Air Serbia respectively.

The investigation is unwelcome news for the Abu Dhabi-owned airline, which seems to be seeking to boost its stake from 29.2% to 49% in Air Berlin (see related story page one).

The EC has also sent a letter to UK government asking to look into the Delta/Virgin Atlantic Airways relationship. Atlanta-based Delta last year acquired a 49% stake in Virgin Atlantic for $360 million from Singapore Airlines as part of its efforts to get greater access to the London Heathrow and strengthen its position on the transatlantic market.

The EC has no concerns on the ownership structure, but it feels that the U.S. airline has effective control of Virgin Atlantic. Delta has three seats on Virgin Atlantic’s seven-member board and CEO Craig Kreeger is a U.S. national.

The Commission has also asked Switzerland to examine Etihad’s purchase of 33.3% of Darwin Airline and to identify whether it is effectively controlled by Swiss national, or rather by the Abu Dhabi airline. Switzerland is not a member of the EU but there is a comprehensive air transport agreement between the European Community and the Swiss Confederation.

“The appointment of an Etihad employee holding a Swiss passport to the board appears to have been devised for no purpose other than compliance with control criteria,” a senior EU official notes.

It has also warned the Italian government that a restructuring of its struggling national carrier Alitalia with the help of Etihad will have to respect the EU rules on ownership and control.