The majority of airlines comply, but fines have been levied, amongst the largest of which was the €1.4m ($1.6m) – at €100 ($112) for every tonne not covered by an allowance – recently paid by Saudia, the Saudi Arabian flag carrier.
Although states are required to reveal the names of carriers fined for ETS breaches, the Saudia fine only came to light via a response to a written question in the Flemish regional government in Belgium.
More surprising, perhaps, was the fact that Saudia paid the fine at all, given reports that its owner, the Saudi government, had ordered it not to comply with ETS.
If non-compliance continues, European states and regional governments can ask the European Commission to impose an operating ban on offenders. Given the hesitancy with which well-known passenger carriers are even named, however, that sanction seems a remote possibility.
Other fierce critics of ETS have been China and India, and operators from both countries have cropped up on lists of non-compliance.
Big name Russian and Chinese carriers are also thought to be ignoring ETS on the orders of their governments, leading Aeroflot to be hit with €215,000 ($240,000) fine by the German authorities, which the flag carrier has appealed.
Airlines had until the end of April this year to surrender their allowances for emissions in 2013 and 2014, so the next few months could see a raft of new fines that dwarf even the record levy on Saudia.