For years, the Pentagon proved slow or altogether unable to accurately inform Congress of the extent of refueling for the Saudi-led campaign—or to fix any issues in its tabulation of assistance. Top military officials also said that the results of American refueling weren’t being monitored: U.S. Central Command chief General Joseph Votel told senators that the U.S. military did not track Saudi or Emirati jets after they were refueled, to see if they carried out strikes that harmed civilians.

It now turns out that there was a lot else they weren’t tracking. It is no coincidence that the Pentagon’s admission came from pressure in the Senate, where legislators have agitated to punish the Saudi regime over Khashoggi’s killing. The sustained pressure signals that the Saudis may not continue to enjoy the level of support from Washington that they have received in years past. In parallel, the Pentagon may also expect further congressional oversight.

“This is good news for U.S. taxpayers and underscores the need for strong oversight of the Department of Defense,” Senator Jack Reed of Rhode Island, the ranking member of the Senate Armed Services Committee, said in a statement. “The Pentagon is taking action to reduce accounting errors of this nature and Congress must continue to be vigilant and fulfill its oversight mission.”

The Pentagon said that the $331 million shortfall was split between $36.8 million in fuel and $294.3 million in U.S. flight hours. It’s unclear how much the Saudis and Emiratis owe individually. In response to a question about whether either had reimbursed the U.S. at all, the Pentagon stated that the “UAE has provided some repayment for refueling services.” The Pentagon later confirmed that the Saudis have not made any payments —a stunning revelation given the amount of attention the campaign has received. The Saudi embassy did not respond to a request for comment. The Emirati ambassador, Yousef Otaiba, told The New York Times on Friday that “the U.A.E. will cover its bills.”

Part of the confusion stemmed from the fact that for the first year of the campaign, the Saudis didn’t have a servicing arrangement, known as an Acquisition and Cross-Servicing Agreement , in place with Washington. Instead, it was funneled fuel— at least according to Pentagon ledgers—via a preexisting servicing agreement that Washington had with the UAE. As of the most recent defense-spending bill, such third-party transfers are now prohibited. In May 2016, a provisional agreement between the U.S. and the Saudis was put in place, but it was never formalized.

“Department of Defense is in the process of seeking reimbursement from KSA and UAE through their respective Acquisition and Cross-Servicing (ACSA) agreements,” said the Pentagon spokesperson Commander Rebecca Rebarich in a statement. “Our partners have been individually notified about our intent to seek reimbursement, and have been given estimates as to how much they owe."