European regulators are seeking comments on proposed remedies from Star Alliance carriers to alleviate competition concerns on the Frankfurt-New York route.
The market test has arisen from European Commission concerns that the co-operation between Lufthansa, United Airlines and Air Canada could result in higher prices on the route for premium passengers.
These carriers have put forward commitments mainly intended to enable competing carriers to start operating - or expand - services between Frankfurt and New York.
Among these commitments is an offer to provide take-off and landing slots at both airports, as well as ease access to connecting traffic.
The Commission is inviting third parties to comment on the proposals, adding that, if the market test suggests they are suitable, the Commission could make them legally-binding on the three Star airlines.