Updated

The struggle to reach a debt deal is hindering efforts to end the partial shutdown of the Federal Aviation Administration, which dragged into its fifth day Wednesday in a partisan standoff between the Democratic-controlled Senate and the Republican-controlled House.

Senate Majority Leader Harry Reid, D-Nev., hasn't taken steps to force a vote on a bill that's necessary to restore the agency's operating authority in part because he doesn't want to tie up the Senate in what could be a time-consuming fight, a leadership aide said. Reid wants to keep the Senate's agenda clear for a quick vote if negotiators settle on a debt deal, said the aide, who asked not to be named because he wasn't authorized to speak publicly.

Democrats also aren't hurrying to force passage of an FAA bill because they expect House Republicans to reject it, the aide said.

The FAA's operating authority expired at midnight on Friday, forcing the furlough of nearly 4,000 employees. Stop-work orders have been issued for more than 150 airport construction projects across the country. About $2.5 billion in grants are being held up because employees who process them have been furloughed.

Sen. Jay Rockefeller, D-W.Va., chairman of the Senate committee that oversees the FAA, blamed a single air carrier — Delta Air Lines — for the shutdown. He said House Republicans were doing Delta's bidding when they sent the Senate a bill last week to extend FAA's operating authority that they knew Democrats would reject because it contained a provision eliminating $16.5 million in air subsidies to rural communities.

The underlying issue, Rockefeller said in a speech to the Senate, is a GOP effort to get Democrats to accept a labor provision in a long-term funding bill for the FAA that primarily benefits Delta. The bill was passed by the House in April. The Senate passed its own funding bill in February without the labor provision.

The labor provision would overturn a National Mediation Board rule approved last year that allows airline and railroad employees to form a union by a simple majority of those voting. Under the old rule, workers who didn't vote were treated as "no" votes.

Republicans complain that the new rule reverses 75 years of precedent to favor labor unions. Democrats and union officials say the change puts airline and railroad elections under the same democratic rules required for unionizing all other companies.

The White House warned in March that President Barack Obama might veto the bill does not include the new rule.

Delta is the only major carrier that is primarily nonunion.

"I wish I understood why the policy objections of one company — Delta Air Lines — mattered so much to so few and also mattered so much more than the livelihood of thousands of American workers who have been or will shortly be furloughed," Rockefeller said.

Delta spokeswoman Gina Laughlin declined to comment directly on Rockefeller's charge.

"Delta appreciates the service of Senator Rockefeller and remains hopeful that he can lead the Senate to work out its differences with the House and reach agreement on a long-term FAA reauthorization," Laughlin said in an email.

Justin Harclerode, a spokesman for the House Transportation and Infrastructure Committee, said that "while it's true the House is interested in ensuring a balanced unionization process, as well as concluding negotiations on the other unresolved issues in the long-term FAA bill, the claim that Republicans are simply doing the bidding of one entity is simply untrue."