BERLIN, (Reuters) – Two European airlines are reviving a dispute over Europe’s takeoff slot regulations. Ryanair has accused Lufthansa Germany of using climate worries to stifle competition.

Major airlines were allowed to keep airport access during the coronavirus epidemic despite the sharp decline in traffic. However, protests came from low-cost counterparts who wanted to increase their presence at once congested airports.

Carsten Spohr (CEO Lufthansa) told a newspaper last week that Lufthansa had to continue operating tens-of-thousands more winter flights to conform to European Union slots usage rules. The result was surplus emissions.

Ryanair is Europe’s most affordable carrier and retorted against the claims Wednesday. He claimed Lufthansa had tried to hinder its rivals during the lengthy dispute over the so-called ghost flight.

Lufthansa CEO Michael O’Leary, of Ryanair Group stated in a statement that they should not operate empty flights so that they can block slots. Instead, Lufthansa must sell the seats from these flights at very low fares to recompense the German and European taxpayers which subsidized them with billions during the COVID Crisis.

Lufthansa spokesperson said that the German airline has never discussed ghost flights. Spohr said to the Frankfurter Allgemeine Sonntagszeitung, December 2012 that the airline would have cut more flights if not for EU policies.

The spokesperson stated that they are talking about the harmonisation European exemptions to allow take-off and land rights to be used in current winter flight plans.

EU rules require airlines to use at least 80 percent of their landing and take-off slots in order for them to be maintained the next year. At the outbreak of COVID-19, the EU had suspended the rules. However, it has begun partially recalibring them to rekindle concerns about the possibility that empty flights may continue.

Lufthansa previously criticized budget airlines like Ryanair Ireland for selling tickets at low prices and artificially increasing demand. Ryanair challenged other legacy carriers to become more competitive.