Delta Air Lines has notified Mesa Air Group that it plans to cancel its contract to fly Bombardier CRJ900s. The notice, sent August 1, marks the second attempt by Delta to remove Mesa-flown jets from its system in recent months. A federal judge in late May issued an injunction barring Delta from ending Mesa’s contract to fly ERJ 145s.

Mesa’s Freedom Airlines subsidiary flies the seven 76-seat CRJ900s in question for Delta from New York JFK Airport. The contract calls for delivery of another seven of the airplanes by next May. Delta, which subleases the airplanes to Mesa for $1 per month, said it based its decision on its regional partner’s poor operational performance. Mesa disputes the claim, and in a statement said it would “vigorously defend its contractual rights.” Nevertheless, Mesa said it would incur no further financial obligation when it returns the airplanes to Delta.