Fatima Basharet 

Associate Editor 

Loyola University Chicago School of Law, JD 2028 

A sky suffocating with carbon must still carry the metal weight of its inhabitants. Every day, more than 100,000 planes release carbon emissions. A solution for this strain on the environment was to build the first market-based compliance framework, holding airlines accountable for any excessive emissions they produced. This framework is the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), which is administered by the International Civil Aviation Organization (ICAO). 

On paper, CORSIA fueled optimism that international environmental accountability for aviation was possible. Airlines were to monitor and report their emissions, and those exceeding an agreed baseline would be required to purchase carbon credits that finance emission reductions elsewhere. In practice, its design provides transgressors with ample room to participate in name while limiting what they actually owe. Through voluntary participation, easy withdrawal, filed differences, and state-by-state enforcement, countries have found ways to stay inside the framework while keeping much of their aviation footprint outside it. CORSIA’s shortcomings expose how weak international environmental accountability remains, leaving aviation emissions free to fly under the radar. 

The enforcement issue 

The enforcement issue facing CORSIA implementation is less about math and more about muscle. CORSIA is a global framework, but enforcement is at the national level. ICAO, like other United Nations specialized agencies, has no independent power to compel a state to act. Each state’s civil aviation authority is responsible for confirming that its airlines purchase and cancel the offset credits they owe. States with close political or economic ties to their national airlines have every incentive to enforce lightly, and CORSIA offers no mechanism to prevent it.  As a result, multinational carriers face a moving compliance target, and the same ton of carbon can be treated very differently depending on the passport of the plane that emitted it. 

Opting in, opting out 

A rule meant to hold an entire industry accountable for something as borderless as the sky should not make escape so easy, yet CORSIA was built with exits from the start. It began as a voluntary program: its monitoring, reporting, and verification (MRV) obligations have applied to airlines since January 2019, but its offsetting obligations bind only states that choose to participate until the mandatory phase begins in 2027. Even then, offsetting generally applies only to routes where both the departure and arrival states participate, so a single non-participating state can exempt an entire route. This loophole widens as more countries decline to join, and mandatory participation in 2027 will not fully close it. States that prefer alternative carbon-offsetting methods can file differences with the ICAO, stepping back from CORSIA’s standards without officially leaving. When states can opt out this easily, accountability becomes a choice rather than a requirement. 

Stuck at the gate 

Even airlines ready to comply may find little to buy. Just as enforcement rests with national regulators, credit supply rests with national governments. Before an airline can use a credit, the host country must authorize it, and most countries have yet to do so. Phase 2, the mandatory phase, makes the carbon credit shortage harder to ignore. Airlines face an estimated 79 million tonnes of offsetting obligations in 2027, but limited programs are approved to supply Phase 2 credits. Europe could narrow that supply even more, with the European Commission proposing tighter eligibility rules for carbon emissions. As obligations grow and eligible credits stay scarce, airlines may struggle to buy their way into compliance. Because CORSIA leaves enforcement to each state, the shortage becomes one more gap that national regulators can choose to overlook rather than close. 

The path forward 

CORSIA was cleared for takeoff without the enforcement power needed to keep it airborne. A framework that states can enforce at their discretion is not a system of international environmental accountability. Lenient regulators, easy exits, and a thin credit market let states treat accountability as optional. CORSIA can still recover, but steadying its flight path requires ICAO to narrow route-based exemptions, strengthen MRV rules, expand the supply of eligible credits, and oversee national enforcement. Without these changes, international environmental accountability will stay grounded, and aviation emissions will keep flying under the radar.