In a dispute between United Healthcare and the trust that provides health insurance for retired Delta Air Lines employees—over what the trust says is more than $5 million in drug rebates it is owed—the judge overseeing the case expressed astonishment Monday that the insurer provided benefits for well over a year while it wrangled over the terms the contract and that the issue of the rebates was still open to interpretation.

During a lengthy hearing on competing motions for summary judgment, U.S. District Judge Mark Cohen also weighed United's request that he dismiss the case as a sanction for some of the trust's board members' destruction of copies of meeting materials after the suit was filed. The insurer argued the shredded documents might contain notes or comments reflecting the board's understanding of the refund issue.

Cohen noted that other copies of the information packages had been turned over to the trust as requested.