Russia and Ukraine are holding indirect talks to reopen a key international air corridor over the Black Sea to commercial flights as part of a plan that could give Ukraine much-needed overflight fees and ease congestion on other crowded air routes, according to five sources familiar with the matter.

The discussions, being brokered on the sidelines of an International Civil Aviation Organization safety meeting this week in Montreal, come amid renewed fighting between Ukrainian government forces and pro-Russian rebels after failed peace talks.

Aviation leaders are seeking to secure a mandate to implement new safety standards after a string of high-profile accidents around the world made 2014 the deadliest year for commercial aviation in almost a decade.