The Tempe, Ariz.-based company set a Feb. 1 deadline for certain conditions to be met or its entire bid would be revoked.
"Right now, we feel very good about our chances of getting this done" despite Delta management's opposition, US Airways Chief Executive Doug Parker said in a conference call with analysts.
His company increased the pressure on Delta's unsecured creditors to take its buyout offer by raising the bid nearly 20 percent to $10.3 billion. Whether the deal would survive regulatory scrutiny may be the deciding factor.
With the deadline set, the ball is now in the creditors' court.
The question is whether they want to take the money US Airways is offering and run the risk of a long regulatory fight, or stick with Delta's plan to emerge from bankruptcy by the middle of this year as a standalone company worth $9.4 billion to $12 billion.
Daniel Golden, a lawyer for Delta's unsecured creditors committee, did not return several phone calls Wednesday seeking comment. Most of the large creditors on the committee have refused to discuss their position publicly, except Delta's pilots union, which opposes the merger.
Delta management has argued that the combination of US Airways and Delta would not receive regulatory approval because of the overlap of the two carriers' routes. US Airways says there wouldn't be any regulatory holdup.
A Jan. 24 hearing has been scheduled by the Senate Committee on Commerce, Science and Transportation on the state of the airline industry and the potential impact of airline mergers.
Ray Neidl, an airline analyst with Calyon Securities in New York, said the increased offer will be more attractive to Delta's creditors, but the great unknown is whether regulators would approve the deal.
"In my opinion, that's going to be the main thing," Neidl said, adding that he gives the US Airways bid a 50-50 chance of being successful.
Parker told analysts Wednesday there's an easy way to know who is right on the regulatory issues.
"Let's just go ask them and find out," Parker said of regulators. Parker was in Washington on Wednesday to talk to lawmakers.
Delta Air Lines Inc. said in a statement Wednesday that its board will do its duty to review the revised offer by US Airways. But, the Atlanta-based airline added, "On its face, the revised proposal does not address significant concerns that have been raised about the initial US Airways proposal and, in fact, would increase the debt burden of the combined company by yet another $1 billion."
Added Kelly Collins, a spokeswoman for Delta's pilots union, "We remain entirely committed to defending our airline from this hostile merger attempt."
US Airways Group Inc. said it would raise its offer by $1.7 billion from its Nov. 15 bid that was currently valued at $8.6 billion.
The decision to increase the offer was reached over the weekend after US Airways officials met to discuss it. On Monday, the carrier's executives met with Gordon Bethune, the former Continental Airlines chief who is working as a consultant to Delta's creditors committee. Bethune urged US Airways to put its best offer forward, according to an official with knowledge of the meeting who spoke on condition of anonymity because of the sensitivity of the talks.
US Airways shares rose $1.10, or 1.9 percent, to $59 in afternoon trading Wednesday on the New York Stock Exchange, boosting the value of the revised offer.
The increased offer comes just two weeks after Parker told The Associated Press that his company had no intention at the time to increase its bid.
Even so, Parker did not exactly rule out at the time the possibility of changing his mind about the price.
Parker said Wednesday that US Airways was raising its offer to remove any doubt that its bid was worth more than Delta's plan to remain a standalone carrier.
Parker said in an interview Wednesday that Delta's creditors committee did not ask US Airways to raise its offer, but it indicated it was having a hard time reaching a decision.
"We just wanted to make it a much, much easier analysis for them, and today we've done that," Parker said.
US Airways said the increased offer is set to expire on Feb. 1 unless creditors indicate support for the start of the due diligence process, which would open up Delta's books to US Airways. US Airways also wants support by the creditors for postponing a Feb. 7 bankruptcy hearing involving Delta's reorganization plan, and it wants the creditors committee to support both companies filing paperwork with the Justice Department that would start the regulatory process.
Parker said "the offer would go away in its entirety" if those conditions were not met.
The increased bid includes 89.5 million shares of US Airways stock and $5 billion in cash. The original offer included 78.5 million shares of US Airways stock and $4 billion in cash.
Based on the Delta's valuation method, US Airways estimated that its increased bid could actually be worth $12.7 billion to $15.4 billion.
Delta's unsecured creditors committee, which will play a key role in deciding the airline's future course, had said prior to Wednesday that it was reviewing both Delta's standalone plan and US Airways' buyout offer.
The committee also has said it would review any offers that came in from other airlines. But as recently as last month, Delta's chief financial officer, Ed Bastian, said there hadn't been any other offers. The Wall Street Journal, citing anonymous sources, reported Wednesday that Delta has been talking with Eagan, Minn.-based Northwest Airlines Corp. about a possible combination. Spokespeople for Delta and Northwest declined to comment.
The Feb. 7 bankruptcy hearing would be to consider approval of Delta's disclosure statement relating to the carrier's standalone reorganization plan.
The disclosure statement includes details on Delta's operations. If the statement is approved, that means Delta can begin soliciting votes on its reorganization plan, which typically takes four to eight weeks.
Parker has said previously that if that hearing were to go forward it could increase the urgency of US Airways' bid because US Airways hopes to consummate its deal to buy Delta before the carrier emerges from Chapter 11.