United Airlines achieved a record profit in the summer peak, mostly driven by low oil prices and a tax windfall.
The carrier reported net income of $4.82 billion, which included a $3.22 billion tax benefit, up from $924 million in the third quarter of 2014.
The low price of fuel helped the company save $1.19 billion.
But revenue got the three months to September 30 fell 2.4% to $10.3 billion from $10.5 billion.
Total passenger revenue was down 3.8% with passenger yield dropping by 5.6% year-on-year
The decline was blamed on a strong US dollar, lower surcharges, reduced travel by business travellers in the energy sector and a softening in domestic yields.
However, operating costs fell by 10.3% to $8.4 billion helped by lower oil prices, improved operational performance and an efficiency drive.
United Airlines’ new chief executive Oscar Munoz suffered a heart attack last week after just over a month in charge.
Munoz took over the role after former boss Jeff Smisek resigned after an investigation into the airline’s relationship with the Port Authority of New York and New Jersey.
The carrier’s general counsel Brett Hart was appointed acting chief executive.
Hart said: “The United family has had a challenging few weeks, but we have never felt more unified and are committed to making the right investments in our people and providing them the tools they need to deliver excellent service to our customers.
“With Oscar Munoz on medical leave, this leadership team and I are working to push forward the agenda we laid out over the past six weeks by focusing on our employees, improving our processes and investing in our systems to further improve our margins.”